diff --git a/docs/collection-return-to-pool.md b/docs/collection-return-to-pool.md
new file mode 100644
index 0000000..e66209a
--- /dev/null
+++ b/docs/collection-return-to-pool.md
@@ -0,0 +1,51 @@
+# Return mistaken collections to the pool
+
+Collection Confirm has a **Return to pool** button on each line and a
+**Return PO to collection pool** button at the bottom of each PO card.
+The PO button affects only the collected lines shown on that card, not
+other lines on the customer order. Both open a confirmation listing the
+affected items before making any changes.
+
+The reset clears driver assignment, collection dates, collected and
+assigned quantities, collection problem flags and the previous AI check.
+Order quantities, costs, SKUs, photos and notes are retained. Customer
+lines return to `item_status = collection_pool`; stock lines return to
+`status = collection_pool` with `quantity_received = 0`. An unbooked stock
+header marked `received` reopens to `sent` so it leaves the accountant's
+booking queue until collection is confirmed again.
+
+Items already invoiced, dispatched, delivered or booked into stock are
+refused. Refused lines are reported separately if some lines can return.
+The browser reloads the queue after the operation. Normal confirmation
+stays available; Add to POS controls are hidden but their underlying
+handlers and endpoints remain.
+
+## Deployment
+
+Deploy **both** the app and `pocketbase/pb_hooks/collection_return.pb.js`.
+The hook is listed in `pocketbase/pb_hooks/DEPLOY`; publish the committed
+hooks folder with `npm run pb:hooks:publish` using the workflow in
+`scripts/pb-hooks/README.md`. No collection fields or select values need
+to be added.
+
+The authenticated capability endpoint
+`GET /api/wfdash/collection-return-guard` must return `{ "version": 1 }`.
+Until the hook is deployed the app refuses resets with HTTP 503. It must
+never fall back to an unguarded update.
+
+Each return uses a PB batch transaction. The hook rechecks row revisions,
+stock parent revisions, invoice metadata and stock ledger entries inside
+that transaction before allowing the writes. It also guards the opposite
+race: a stale customer confirmation cannot advance a returned/assigned
+line, and a stock booking cannot insert a receipt after the PO reopens.
+Existing PB audit hooks record customer field changes; no extra app audit
+notes are added.
+
+## Validation
+
+Run the tests under `src/components/collection-confirm`,
+`src/app/(app)/collection-confirm`, `src/app/api/v1/collection-confirm`,
+and `src/lib/server/collection-return*.test.ts`. The hook tests evaluate
+the real JS file in a mocked PB environment; they do not change live data.
+After deployment, verify a mistaken collection returns to the pool with
+zero collected quantity and can be assigned to a driver again.
diff --git a/pocketbase/pb_hooks/DEPLOY b/pocketbase/pb_hooks/DEPLOY
index 2180c78..eccd6f3 100644
--- a/pocketbase/pb_hooks/DEPLOY
+++ b/pocketbase/pb_hooks/DEPLOY
@@ -8,3 +8,4 @@
 quotes.pb.js
 audit_log_utils.js
 audit_log.pb.js
+collection_return.pb.js
diff --git a/pocketbase/pb_hooks/collection_return.pb.js b/pocketbase/pb_hooks/collection_return.pb.js
new file mode 100644
index 0000000..763a432
--- /dev/null
+++ b/pocketbase/pb_hooks/collection_return.pb.js
@@ -0,0 +1,94 @@
+/**
+ * Revision checks for the Collection Confirm return-to-pool batch.
+ * PB runs each child record request (and these hooks) inside the batch's
+ * database transaction. A concurrent confirm/invoice/booking therefore
+ * either precedes these checks or follows the complete reset; it cannot
+ * slip between validation and the writes. Ordinary updates are untouched.
+ * Deploy with the app; the service refuses resets without this capability.
+ */
+routerAdd("GET", "/api/wfdash/collection-return-guard", (e) => {
+  return e.json(200, { version: 1 });
+}, $apis.requireSuperuserAuth());
+
+onRecordUpdateRequest((e) => {
+  const info = e.requestInfo();
+  const guard = info.body && info.body._collection_return_guard;
+  if (!guard) {
+    // A confirmer may have read the row before a return committed. Check
+    // its current state and save together, so it cannot resurrect a pickup.
+    if (e.record.collection().name === "order_items" && info.body && info.body.item_status === "ready_invoice") {
+      const originalApp = e.app;
+      try {
+        return originalApp.runInTransaction((txApp) => {
+          e.app = txApp;
+          const latest = JSON.parse(JSON.stringify(txApp.findRecordById("order_items", e.record.id || e.record.original().id)));
+          const original = JSON.parse(JSON.stringify(e.record.original()));
+          if (latest.updated !== original.updated || ["collection_pool", "assigned"].indexOf(latest.item_status) !== -1) {
+            throw new BadRequestError("Collection changed. Refresh before confirming for invoicing.");
+          }
+          return e.next();
+        });
+      } finally { e.app = originalApp; }
+    }
+    return e.next();
+  }
+  if (!e.auth || !e.auth.isSuperuser()) throw new ForbiddenError("Collection resets require the server.");
+  if (info.context !== "batch") throw new BadRequestError("Collection resets must run in a batch transaction.");
+
+  const current = JSON.parse(JSON.stringify(e.record.original()));
+  if (!guard.updated || current.updated !== guard.updated) {
+    throw new BadRequestError("This item changed. Refresh Collection Confirm and try again.");
+  }
+  const collection = e.record.collection().name;
+  let refType = "order_item";
+  let refId = current.id;
+  if (collection === "order_items") {
+    let details = current.order_item_details;
+    if (typeof details === "string") {
+      try { details = JSON.parse(details); } catch (_) { details = null; }
+    }
+    const invoice = details && details.invoice;
+    const billed = invoice && (invoice.qbInvoiceId || invoice.qbInvoiceLink || invoice.billingCompany);
+    const downstream = ["qty_invoiced", "qty_delivered", "qty_stocked", "qty_picked", "qty_loaded", "surplus_qty"]
+      .some((field) => Number(current[field] || 0) > 0);
+    if (current.item_status !== "collected" || downstream || billed || current.customer_invoice_number ||
+        current.delivery_note_number || current.invoiced_date || current.delivered_at || current.stock_booked_from) {
+      throw new BadRequestError("This item has moved on and cannot be returned to the collection pool.");
+    }
+  } else {
+    let parent = current;
+    if (collection === "stock_purchase_items") {
+      if (current.status !== "collected" || !current.purchase) throw new BadRequestError("Stock item is no longer collected.");
+      parent = JSON.parse(JSON.stringify(e.app.findRecordById("stock_purchases", current.purchase)));
+      if (!guard.parent_updated || parent.updated !== guard.parent_updated) throw new BadRequestError("Stock PO changed. Refresh before returning it.");
+    }
+    if (parent.booked_at || ["sent", "received"].indexOf(parent.status) === -1) {
+      throw new BadRequestError("Stock PO is booked or no longer open for collection.");
+    }
+    refType = "stock_purchase";
+    refId = parent.id;
+  }
+  const ledger = e.app.findRecordsByFilter("stock_ledger",
+    "reference_type = {:type} && reference_id = {:id}", "", 1, 0,
+    { type: refType, id: refId });
+  if (ledger.length) throw new BadRequestError("A stock booking exists; collection cannot be reset.");
+  return e.next();
+}, "order_items", "stock_purchase_items", "stock_purchases");
+
+// Booking writes the ledger before inventory. If it read the old received
+// quantities before a return, reject its first write after the PO reopens.
+// Conversely, a committed ledger entry makes the return guard refuse.
+onRecordCreateRequest((e) => {
+  if (e.record.getString("reference_type") !== "stock_purchase") return e.next();
+  const originalApp = e.app;
+  try {
+    return originalApp.runInTransaction((txApp) => {
+      e.app = txApp;
+      const purchase = JSON.parse(JSON.stringify(txApp.findRecordById("stock_purchases", e.record.getString("reference_id"))));
+      if (purchase.status !== "received" || purchase.booked_at) {
+        throw new BadRequestError("Stock PO is no longer awaiting booking. Refresh before trying again.");
+      }
+      return e.next();
+    });
+  } finally { e.app = originalApp; }
+}, "stock_ledger");
diff --git a/src/app/(app)/collection-confirm/page-ai.test.tsx b/src/app/(app)/collection-confirm/page-ai.test.tsx
index 856ed5a..97765a1 100644
--- a/src/app/(app)/collection-confirm/page-ai.test.tsx
+++ b/src/app/(app)/collection-confirm/page-ai.test.tsx
@@ -72,12 +72,12 @@ function setupFetch(opts: { confirmOk: boolean }) {
   });
 }
 
-async function openConfirmAndAdd() {
+async function openConfirm() {
   const user = userEvent.setup();
   render(<Page />);
   await waitFor(() => expect(screen.getByTestId("po-card-PO-1")).toBeInTheDocument());
   await user.click(screen.getByTestId("po-card-toggle-PO-1"));
-  await user.click(screen.getByTestId("po-card-confirm-add-pos-PO-1"));
+  await user.click(screen.getByTestId("po-card-confirm-PO-1"));
   const dialog = await screen.findByRole("dialog");
   // Pre-filled from ai_check.
   expect(within(dialog).getByLabelText(/Supplier invoice number/i)).toHaveValue("5028256");
@@ -94,20 +94,19 @@ describe("CollectionConfirmPage AI handlers", () => {
     addResults = [{ row_id: "row-a", status: "created", stock_item_id: "s" }];
   });
 
-  it("toasts added / failed / need-a-SKU counts after Add to POS", async () => {
-    addResults = [
-      { row_id: "row-a", status: "created", stock_item_id: "s" },
-      { row_id: "row-c", status: "failed", stock_item_id: null, error: "boom" },
-      { row_id: "row-x", status: "needs_sku", stock_item_id: null },
-    ];
+  it("hides Add to POS and keeps normal confirmation", async () => {
     setupFetch({ confirmOk: true });
-    await openConfirmAndAdd();
-    await waitFor(() => expect(toastMock.warning).toHaveBeenCalledWith("1 added, 1 failed, 1 needs a SKU"));
+    const user = userEvent.setup();
+    render(<Page />);
+    await screen.findByTestId("po-card-PO-1");
+    await user.click(screen.getByTestId("po-card-toggle-PO-1"));
+    expect(screen.queryByRole("button", { name: /add to pos/i })).not.toBeInTheDocument();
+    expect(screen.getByTestId("po-card-confirm-PO-1")).toBeInTheDocument();
   });
 
   it("does not add to the POS when the confirm fails", async () => {
     const spy = setupFetch({ confirmOk: false });
-    await openConfirmAndAdd();
+    await openConfirm();
     await waitFor(() =>
       expect(spy.mock.calls.some(([a]) => fetchUrl(a) === "/api/v1/order-items/confirm")).toBe(true),
     );
@@ -115,17 +114,55 @@ describe("CollectionConfirmPage AI handlers", () => {
     expect(addCalls(spy)).toHaveLength(0);
   });
 
-  it("adds only the not-in-POS customer rows, once, after the confirm succeeds", async () => {
+  it("does not add to POS after normal confirmation succeeds", async () => {
     const spy = setupFetch({ confirmOk: true });
-    await openConfirmAndAdd();
-    await waitFor(() => expect(addCalls(spy)).toHaveLength(1));
-    const [, init] = addCalls(spy)[0];
-    expect(JSON.parse(String((init as RequestInit).body))).toEqual({ row_ids: ["row-a", "row-c"] });
-    expect((init as RequestInit).headers).toMatchObject({ Authorization: "Bearer tok-123" });
-    const order = spy.mock.calls.map(([a]) => fetchUrl(a));
-    expect(order.indexOf("/api/v1/order-items/confirm")).toBeLessThan(
-      order.indexOf("/api/v1/collection-confirm/add-to-pos"),
-    );
+    await openConfirm();
+    await waitFor(() => expect(toastMock.success).toHaveBeenCalled());
+    expect(addCalls(spy)).toHaveLength(0);
+  });
+
+  it.each([false, true])("returns the selected line or PO and refreshes the queue (whole PO: %s)", async (wholePo) => {
+    const spy = setupFetch({ confirmOk: true });
+    let returned = false;
+    const base = spy.getMockImplementation()!;
+    spy.mockImplementation(async (input, init) => {
+      if (fetchUrl(input) === "/api/v1/collection-confirm/return-to-pool") {
+        returned = true;
+        return jsonResponse({ returned: wholePo ? rows : [rows[0]], skipped: [] });
+      }
+      if (fetchUrl(input) === "/api/v1/collection-confirm" && returned) {
+        return jsonResponse({ items: wholePo ? [] : rows.slice(1) });
+      }
+      return base(input, init);
+    });
+    const user = userEvent.setup();
+    render(<Page />);
+    await screen.findByTestId("po-card-PO-1");
+    await user.click(screen.getByTestId("po-card-toggle-PO-1"));
+    await user.click(screen.getByTestId(wholePo ? "po-card-return-pool-PO-1" : "return-to-pool-row-a"));
+    const dialog = screen.getByRole("dialog");
+    await user.click(within(dialog).getByRole("button", { name: wholePo ? "Return 3 items" : "Return 1 item" }));
+    await waitFor(() => expect(screen.queryByTestId("items-row-row-a")).not.toBeInTheDocument());
+    const call = spy.mock.calls.find(([input]) => fetchUrl(input) === "/api/v1/collection-confirm/return-to-pool")!;
+    expect(JSON.parse(String(call[1]?.body))).toEqual({ rows: (wholePo ? rows : [rows[0]]).map(row => ({ id: row.id, source: "customer" })) });
+    expect(call[1]?.headers).toMatchObject({ Authorization: "Bearer tok-123" });
+    expect(toastMock.success).toHaveBeenCalledWith(expect.stringContaining("Ready for driver assignment"));
+  });
+
+  it("keeps the reset dialog open when the server refuses the return", async () => {
+    const spy = setupFetch({ confirmOk: true });
+    const base = spy.getMockImplementation()!;
+    spy.mockImplementation(async (input, init) => fetchUrl(input) === "/api/v1/collection-confirm/return-to-pool"
+      ? jsonResponse({ returned: [], skipped: [{ id: "row-a", reason: "Already invoiced" }] }, { ok: false, status: 409 })
+      : base(input, init));
+    const user = userEvent.setup();
+    render(<Page />);
+    await screen.findByTestId("po-card-PO-1");
+    await user.click(screen.getByTestId("po-card-toggle-PO-1"));
+    await user.click(screen.getByTestId("return-to-pool-row-a"));
+    await user.click(screen.getByRole("button", { name: "Return 1 item" }));
+    expect(await screen.findByRole("alert")).toHaveTextContent("Already invoiced");
+    expect(screen.getByTestId("items-row-row-a")).toBeInTheDocument();
   });
 
   it("Check with AI posts { po_number } with the Bearer header", async () => {
diff --git a/src/app/(app)/collection-confirm/page.tsx b/src/app/(app)/collection-confirm/page.tsx
index 95d6241..9aa8dd8 100644
--- a/src/app/(app)/collection-confirm/page.tsx
+++ b/src/app/(app)/collection-confirm/page.tsx
@@ -454,6 +454,34 @@ export default function CollectionConfirmPage() {
     [authedJsonHeaders, load],
   );
 
+  const handleReturnToPool = useCallback(async (selected: ConfirmRow[]) => {
+    const response = await fetch("/api/v1/collection-confirm/return-to-pool", {
+      method: "POST",
+      headers: authedJsonHeaders(),
+      body: JSON.stringify({ rows: selected.map(row => ({ id: row.id, source: row.source === "stock" ? "stock" : "customer" })) }),
+    });
+    const data = await response.json().catch(() => ({})) as {
+      returned?: Array<{ id: string }>;
+      skipped?: Array<{ id: string; reason: string }>;
+      error?: string;
+    };
+    if (!response.ok) {
+      await load({ silent: true });
+      throw new Error(data.error || data.skipped?.map(row => row.reason).join(" ") || "Could not return these items.");
+    }
+    const count = data.returned?.length ?? 0;
+    toast.success(`Returned ${count} item${count === 1 ? "" : "s"} to the collection pool. Ready for driver assignment.`);
+    if (data.skipped?.length) {
+      toast.warning(`${data.skipped.length} item(s) could not be returned: ${data.skipped.map(row => row.reason).join(" ")}`);
+    }
+    setCostOverrides(previous => {
+      const next = { ...previous };
+      for (const row of data.returned ?? []) delete next[row.id];
+      return next;
+    });
+    await load({ silent: true });
+  }, [authedJsonHeaders, load]);
+
   const handleCheckWithAi = useCallback(
     async (poNumber: string) => {
       try {
@@ -839,6 +867,7 @@ export default function CollectionConfirmPage() {
                   onSkuChange={(id, sku) => void handleSkuChange(id, sku)}
                   onQtyChange={(id, qty) => void handleQtyChange(id, qty)}
                   onClearRows={(payload) => handleClearRows(group, payload)}
+                  onReturnToPool={handleReturnToPool}
                   onAddToPos={(rowId) => void handleAddToPos([rowId])}
                   onCheckWithAi={() => handleCheckWithAi(group.poNumber)}
                   onMovePhoto={handleMovePhoto}
diff --git a/src/app/api/v1/collection-confirm/return-to-pool/route.test.ts b/src/app/api/v1/collection-confirm/return-to-pool/route.test.ts
new file mode 100644
index 0000000..bfc00d8
--- /dev/null
+++ b/src/app/api/v1/collection-confirm/return-to-pool/route.test.ts
@@ -0,0 +1,52 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { NextRequest } from "next/server";
+
+vi.mock("@/lib/server/browser-session", () => ({ getBrowserSessionUser: vi.fn() }));
+vi.mock("@/lib/server/collection-return-service", () => ({ returnCollectedToPool: vi.fn() }));
+import { getBrowserSessionUser } from "@/lib/server/browser-session";
+import { returnCollectedToPool } from "@/lib/server/collection-return-service";
+import { POST } from "./route";
+
+const rows = [{ id: "item1", source: "customer" as const }, { id: "stock1", source: "stock" as const }];
+const req = (body: unknown) => new NextRequest("http://localhost/api/v1/collection-confirm/return-to-pool", {
+  method: "POST", body: JSON.stringify(body), headers: { Authorization: "Bearer token", "content-type": "application/json" },
+});
+beforeEach(() => {
+  vi.clearAllMocks();
+  vi.mocked(getBrowserSessionUser).mockResolvedValue({ id: "buyer", name: "Buyer", user_type: [] });
+  vi.mocked(returnCollectedToPool).mockResolvedValue({ returned: rows, skipped: [] });
+});
+
+describe("POST collection-confirm/return-to-pool", () => {
+  it("requires a real browser session", async () => {
+    vi.mocked(getBrowserSessionUser).mockRejectedValue(Object.assign(new Error("Not authenticated."), { status: 401 }));
+    expect((await POST(req({ rows }))).status).toBe(401);
+    expect(returnCollectedToPool).not.toHaveBeenCalled();
+  });
+
+  it.each([null, {}, { rows: [] }, { rows: [{ id: "x", source: "orders" }] }, { rows: [null] }, { rows: [{ id: " ", source: "stock" }] }, { rows: Array(501).fill(rows[0]) }])("rejects invalid selection %#", async (body) => {
+    expect((await POST(req(body))).status).toBe(400);
+    expect(returnCollectedToPool).not.toHaveBeenCalled();
+  });
+
+  it("uses the authenticated actor, never an actor supplied in the body", async () => {
+    const res = await POST(req({ rows, actor: { id: "forged" } }));
+    expect(res.status).toBe(200);
+    expect(returnCollectedToPool).toHaveBeenCalledWith(rows, { id: "buyer", name: "Buyer" });
+    expect(await res.json()).toEqual({ returned: rows, skipped: [] });
+  });
+
+  it("reports refused selections as conflicts", async () => {
+    vi.mocked(returnCollectedToPool).mockResolvedValue({ returned: [], skipped: [{ ...rows[0], reason: "Already invoiced" }] });
+    const res = await POST(req({ rows }));
+    expect(res.status).toBe(409);
+    expect((await res.json()).skipped[0].reason).toBe("Already invoiced");
+  });
+
+  it("does not leak backend errors", async () => {
+    vi.mocked(returnCollectedToPool).mockRejectedValue(new Error("internal secret"));
+    const res = await POST(req({ rows }));
+    expect(res.status).toBe(500);
+    expect(JSON.stringify(await res.json())).not.toContain("internal secret");
+  });
+});
diff --git a/src/app/api/v1/collection-confirm/return-to-pool/route.ts b/src/app/api/v1/collection-confirm/return-to-pool/route.ts
new file mode 100644
index 0000000..82096bd
--- /dev/null
+++ b/src/app/api/v1/collection-confirm/return-to-pool/route.ts
@@ -0,0 +1,25 @@
+import { NextRequest, NextResponse } from "next/server";
+import { getBrowserSessionUser } from "@/lib/server/browser-session";
+import { returnCollectedToPool, type CollectionReturnRow } from "@/lib/server/collection-return-service";
+
+export const runtime = "nodejs";
+export const dynamic = "force-dynamic";
+
+export async function POST(req: NextRequest) {
+  try {
+    const user = await getBrowserSessionUser(req);
+    const body = await req.json().catch(() => null) as { rows?: unknown } | null;
+    const rows = body?.rows;
+    if (!Array.isArray(rows) || !rows.length || rows.length > 500 || rows.some(r =>
+      !r || typeof r.id !== "string" || !r.id.trim() || !["customer", "stock"].includes(r.source),
+    )) {
+      return NextResponse.json({ error: "Choose between 1 and 500 collected items." }, { status: 400 });
+    }
+    const result = await returnCollectedToPool(rows as CollectionReturnRow[], { id: user.id, name: user.name });
+    return NextResponse.json(result, { status: result.returned.length ? 200 : 409 });
+  } catch (err) {
+    const status = (err as { status?: number }).status || 500;
+    if (status >= 500) console.error("[collection-confirm/return-to-pool]", err);
+    return NextResponse.json({ error: status >= 500 ? "Could not return these items. Refresh and try again." : err instanceof Error ? err.message : "Return failed." }, { status });
+  }
+}
diff --git a/src/components/collection-confirm/items-table.tsx b/src/components/collection-confirm/items-table.tsx
index 2876b19..0fb21d3 100644
--- a/src/components/collection-confirm/items-table.tsx
+++ b/src/components/collection-confirm/items-table.tsx
@@ -7,6 +7,7 @@ import {
   CheckCircle2,
   MinusCircle,
   Pencil,
+  Undo2,
   XCircle,
 } from "lucide-react";
 import { useState } from "react";
@@ -35,6 +36,7 @@ type Props = {
   onQtyChange?: (id: string, qty: number) => void;
   /** "Add to POS" click for a line that is not in the POS yet. */
   onAddToPos?: (rowId: string) => void;
+  onReturnToPool?: (row: ConfirmRow) => void;
   /**
    * Force the AI + POS columns on or off. By default the AI column shows
    * only when some row carries an `ai_check`, and the POS column when some
@@ -213,6 +215,7 @@ export function ItemsTable({
   onSkuChange,
   onQtyChange,
   onAddToPos,
+  onReturnToPool,
   showAi,
 }: Props) {
   const aiColumn = showAi ?? rows.some((r) => !!r.ai_check);
@@ -413,6 +416,17 @@ export function ItemsTable({
                 <span className="line-clamp-2">
                   {row.description ?? row.po_description ?? "—"}
                 </span>
+                {onReturnToPool ? (
+                  <button
+                    type="button"
+                    className="mt-1 inline-flex min-h-8 items-center gap-1 rounded px-1.5 text-xs font-medium text-muted-foreground hover:bg-accent hover:text-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring"
+                    onClick={() => onReturnToPool(row)}
+                    aria-label={`Return ${row.description || row.sku || row.id} to collection pool`}
+                    data-testid={`return-to-pool-${row.id}`}
+                  >
+                    <Undo2 className="size-3.5" aria-hidden /> Return to pool
+                  </button>
+                ) : null}
                 {/* AI ticks and POS status sit under the description, not in
                     extra columns: the table shares its pane with the document
                     preview, and trailing columns ended up hidden behind it. */}
diff --git a/src/components/collection-confirm/po-card-ai.test.tsx b/src/components/collection-confirm/po-card-ai.test.tsx
index 894ec5a..e5c2565 100644
--- a/src/components/collection-confirm/po-card-ai.test.tsx
+++ b/src/components/collection-confirm/po-card-ai.test.tsx
@@ -214,13 +214,13 @@ describe("PoCard AI layer", () => {
     await waitFor(() => expect(btn).not.toBeDisabled());
   });
 
-  it("renders Confirm and add to POS only when a customer row is not in POS", async () => {
+  it("hides the POS actions even when their handlers are supplied", () => {
     const onGo = vi.fn();
     const { rerender } = render(
-      <PoCard rows={[makeAiRow({ in_pos: false })]} {...props} onConfirmAndAddToPos={onGo} />,
+      <PoCard rows={[makeAiRow({ in_pos: false })]} {...props} onConfirmAndAddToPos={onGo} onAddToPos={onGo} />,
     );
-    await userEvent.click(screen.getByRole("button", { name: /confirm and add to pos/i }));
-    expect(onGo).toHaveBeenCalledTimes(1);
+    expect(screen.queryByRole("button", { name: /add to pos/i })).not.toBeInTheDocument();
+    expect(screen.getByRole("button", { name: /^confirm for invoicing$/i })).toBeInTheDocument();
 
     rerender(
       <PoCard
@@ -231,4 +231,25 @@ describe("PoCard AI layer", () => {
     );
     expect(screen.queryByRole("button", { name: /confirm and add to pos/i })).not.toBeInTheDocument();
   });
+
+  it("returns one selected line only after confirming the reset", async () => {
+    const onReturnToPool = vi.fn().mockResolvedValue(undefined);
+    const row = makeAiRow({ id: "chosen", source: "stock" });
+    render(<PoCard rows={[row, { ...plain, id: "other" }]} {...props} onReturnToPool={onReturnToPool} />);
+    await userEvent.click(screen.getByTestId("return-to-pool-chosen"));
+    expect(onReturnToPool).not.toHaveBeenCalled();
+    const dialog = screen.getByRole("dialog");
+    expect(dialog).toHaveTextContent("Collected quantities will be reset to zero");
+    await userEvent.click(screen.getByRole("button", { name: "Return 1 item" }));
+    expect(onReturnToPool).toHaveBeenCalledWith([row]);
+  });
+
+  it("offers all the card's collected rows in the PO footer and allows cancelling", async () => {
+    const onReturnToPool = vi.fn();
+    render(<PoCard rows={[plain, { ...plain, id: "second", source: "stock" }]} {...props} onReturnToPool={onReturnToPool} />);
+    await userEvent.click(screen.getByTestId("po-card-return-pool-PO-1"));
+    expect(screen.getByRole("button", { name: "Return 2 items" })).toBeInTheDocument();
+    await userEvent.click(screen.getByRole("button", { name: "Cancel" }));
+    expect(onReturnToPool).not.toHaveBeenCalled();
+  });
 });
diff --git a/src/components/collection-confirm/po-card.tsx b/src/components/collection-confirm/po-card.tsx
index 16f2d3f..139c5f2 100644
--- a/src/components/collection-confirm/po-card.tsx
+++ b/src/components/collection-confirm/po-card.tsx
@@ -26,6 +26,7 @@ import { InvoiceViewer } from "./invoice-viewer";
 import { ItemsTable } from "./items-table";
 import { ClearPanel, type ClearPayload } from "./clear-panel";
 import type { Attachment } from "./photo-strip";
+import { ReturnToPoolDialog } from "./return-to-pool-dialog";
 
 /**
  * Viewport-width probe — returns `true` when the viewport is ≥
@@ -141,6 +142,8 @@ type Props = {
   onCheckWithAi?: () => Promise<void>;
   /** Confirm for invoicing, then add every not-in-POS customer line to the POS. */
   onConfirmAndAddToPos?: () => void;
+  /** Return only these collected rows to the pool for a fresh driver assignment. */
+  onReturnToPool?: (rows: ConfirmRow[]) => Promise<void>;
   /** Delete a wrongly uploaded or duplicate photo (the one open in the previewer). */
   onDeletePhoto?: (target: NonNullable<Attachment["deleteTarget"]>) => Promise<void>;
   /** Move a driver photo whose invoice names another PO onto that PO. */
@@ -200,13 +203,13 @@ export function PoCard({
   onPopOut,
   onFullscreen,
   onInvoiceUpload,
-  onAddToPos,
   onCheckWithAi,
-  onConfirmAndAddToPos,
+  onReturnToPool,
   onMovePhoto,
   onDeletePhoto,
 }: Props) {
   const itemCount = rows.length;
+  const [returnRows, setReturnRows] = useState<ConfirmRow[] | null>(null);
   const [checkingAi, setCheckingAi] = useState(false);
   const [docPanelOpen, setDocPanelOpen] = useState(false);
   const aiDoc = useMemo(() => cardDocument(rows), [rows]);
@@ -245,7 +248,6 @@ export function PoCard({
       : [...paired.values()].sort((a, b) => a.line_no - b.line_no);
     return { aiDocLines: all, matchedLineNos: new Set(paired.keys()) };
   }, [rows, aiDoc]);
-  const hasUnpostedCustomerRows = rows.some((r) => r.source !== "stock" && !r.in_pos);
   const aiDocPanel =
     docPanelOpen && aiDoc ? (
       <DocumentLinesPanel poNumber={poNumber} lines={aiDocLines} matchedLineNos={matchedLineNos} />
@@ -893,7 +895,7 @@ export function PoCard({
                   onCostChange={onCostChange}
                   onSkuChange={onSkuChange}
                   onQtyChange={onQtyChange}
-                  onAddToPos={onAddToPos}
+                  onReturnToPool={onReturnToPool ? (row) => setReturnRows([row]) : undefined}
                 />
                 </div>
               </div>
@@ -960,7 +962,7 @@ export function PoCard({
                   onCostChange={onCostChange}
                   onSkuChange={onSkuChange}
                   onQtyChange={onQtyChange}
-                  onAddToPos={onAddToPos}
+                  onReturnToPool={onReturnToPool ? (row) => setReturnRows([row]) : undefined}
                 />
               </div>
 
@@ -1021,11 +1023,11 @@ export function PoCard({
 
           <AiFindings findings={aiFindings} notes={aiNotes} />
 
-          <footer className="flex items-center justify-between gap-2">
+          <footer className="flex flex-wrap items-center justify-between gap-2">
             <p className="hidden text-[11px] text-muted-foreground lg:block">
               Drag the divider to give the invoice more room.
             </p>
-            <div className="ml-auto flex gap-2">
+            <div className="ml-auto flex flex-wrap justify-end gap-2">
               {onCheckWithAi ? (
                 <Button
                   type="button"
@@ -1067,19 +1069,23 @@ export function PoCard({
                   Confirm for invoicing
                 </Button>
               ) : null}
-              {hasCustomerRows && hasUnpostedCustomerRows && onConfirmAndAddToPos ? (
+              {onReturnToPool ? (
                 <Button
                   type="button"
-                  onClick={onConfirmAndAddToPos}
-                  data-testid={`po-card-confirm-add-pos-${poNumber}`}
+                  variant="outline"
+                  onClick={() => setReturnRows(rows.slice())}
+                  data-testid={`po-card-return-pool-${poNumber}`}
                 >
-                  Confirm and add to POS
+                  Return PO to collection pool
                 </Button>
               ) : null}
             </div>
           </footer>
         </div>
       ) : null}
+      {returnRows && onReturnToPool ? (
+        <ReturnToPoolDialog rows={returnRows} poNumber={poNumber} onClose={() => setReturnRows(null)} onSubmit={onReturnToPool} />
+      ) : null}
     </section>
   );
 }
diff --git a/src/components/collection-confirm/return-to-pool-dialog.tsx b/src/components/collection-confirm/return-to-pool-dialog.tsx
new file mode 100644
index 0000000..e5355d6
--- /dev/null
+++ b/src/components/collection-confirm/return-to-pool-dialog.tsx
@@ -0,0 +1,56 @@
+"use client";
+
+import { useState } from "react";
+import { Loader2 } from "lucide-react";
+import { Button } from "@/components/ui/button";
+import { ModalShell } from "@/components/ui/modal-shell";
+import type { ConfirmRow } from "@/lib/server/collection-confirm-service";
+
+export function ReturnToPoolDialog({ rows, poNumber, onClose, onSubmit }: {
+  rows: ConfirmRow[];
+  poNumber: string;
+  onClose: () => void;
+  onSubmit: (rows: ConfirmRow[]) => Promise<void>;
+}) {
+  const [busy, setBusy] = useState(false);
+  const [error, setError] = useState<string | null>(null);
+  const count = rows.length;
+  return (
+    <ModalShell.Dialog
+      open
+      onOpenChange={(open) => { if (!open && !busy) onClose(); }}
+      size="md"
+      eyebrow={poNumber}
+      title="Return to collection pool?"
+      description={`Return ${count} collected item${count === 1 ? "" : "s"} for another pickup.`}
+      footer={
+        <div className="flex justify-end gap-2">
+          <Button variant="outline" disabled={busy} onClick={onClose}>Cancel</Button>
+          <Button disabled={busy} onClick={async () => {
+            setBusy(true);
+            setError(null);
+            try {
+              await onSubmit(rows);
+              onClose();
+            } catch (err) {
+              setError(err instanceof Error ? err.message : "Could not return these items.");
+            } finally { setBusy(false); }
+          }}>
+            {busy ? <Loader2 className="size-4 animate-spin" /> : null}
+            {busy ? "Returning…" : `Return ${count} item${count === 1 ? "" : "s"}`}
+          </Button>
+        </div>
+      }
+    >
+      <p className="text-sm text-muted-foreground">
+        Collected quantities will be reset to zero and driver assignments and collection dates cleared.
+        These items will be available to assign to a driver again. Photos and order details will be kept.
+      </p>
+      <ul className="max-h-48 space-y-1 overflow-auto text-sm">
+        {rows.map(row => <li key={`${row.source}:${row.id}`}>{row.description || row.po_description || row.sku || row.id}</li>)}
+      </ul>
+      <p className="text-xs text-muted-foreground">Items already invoiced, dispatched or booked into stock cannot be returned here.</p>
+      {error ? <p role="alert" className="text-sm text-destructive">{error}</p> : null}
+    </ModalShell.Dialog>
+  );
+}
diff --git a/src/lib/server/collection-return-guard.test.ts b/src/lib/server/collection-return-guard.test.ts
new file mode 100644
index 0000000..ce442c6
--- /dev/null
+++ b/src/lib/server/collection-return-guard.test.ts
@@ -0,0 +1,114 @@
+// Run the real PB hook in a JS sandbox; no live records are changed.
+import { readFileSync } from "node:fs";
+import { runInNewContext } from "node:vm";
+import { describe, expect, it, vi } from "vitest";
+
+function setup(stored: Record<string, unknown> = {}, collection = "order_items") {
+  let hook!: (event: unknown) => void;
+  let capability!: (event: unknown) => void;
+  let createHook!: (event: unknown) => void;
+  const next = vi.fn();
+  const body = { _collection_return_guard: { updated: "v1", parent_updated: "p1" } };
+  const parent = { id: "po1", updated: "p1", status: "received", booked_at: "" };
+  const app = {
+    findRecordById: vi.fn((name: string) => name === "stock_purchases" ? parent : original),
+    findRecordsByFilter: vi.fn((): unknown[] => []),
+    runInTransaction: (fn: (tx: unknown) => void) => fn(app),
+  };
+  const info = { body, context: "batch" };
+  const original = { id: "row1", updated: "v1", item_status: "collected", status: "collected", purchase: "po1", ...stored };
+  const e = {
+    requestInfo: () => info, auth: { isSuperuser: () => true }, app, next,
+    record: { original: () => original, collection: () => ({ name: collection }), getString: (field: string) => String((original as Record<string, unknown>)[field] ?? "") },
+  };
+  const source = readFileSync("pocketbase/pb_hooks/collection_return.pb.js", "utf8");
+  runInNewContext(source, {
+    onRecordUpdateRequest: (callback: typeof hook) => { hook = callback; },
+    onRecordCreateRequest: (callback: typeof hook) => { createHook = callback; },
+    routerAdd: (_method: string, _path: string, callback: typeof capability) => { capability = callback; },
+    $apis: { requireSuperuserAuth: () => ({}) },
+    BadRequestError: Error, ForbiddenError: Error,
+  });
+  return { call: () => hook(e), create: () => createHook(e), e, next, app, info, parent, capability, original };
+}
+
+describe("PB collection return transaction guard", () => {
+  it("allows a matching collected revision inside a batch", () => {
+    const test = setup();
+    test.call();
+    expect(test.next).toHaveBeenCalledOnce();
+  });
+  it("leaves ordinary updates alone", () => {
+    const test = setup();
+    test.info.body = {} as typeof test.info.body;
+    test.call();
+    expect(test.next).toHaveBeenCalledOnce();
+  });
+  it.each([
+    { updated: "v2" }, { item_status: "ready_invoice" }, { qty_delivered: 1 },
+    { order_item_details: { invoice: { number: "INV1", qbInvoiceId: "qb1" } } },
+    { order_item_details: JSON.stringify({ invoice: { number: "INV1", billingCompany: "CNL" } }) },
+  ])("refuses a concurrent advance: %j", stored => {
+    const test = setup(stored);
+    expect(test.call).toThrow();
+    expect(test.next).not.toHaveBeenCalled();
+  });
+  it("refuses non-batch resets", () => {
+    const test = setup();
+    test.info.context = "default";
+    expect(test.call).toThrow();
+  });
+  it("refuses non-superusers", () => {
+    const test = setup();
+    test.e.auth.isSuperuser = () => false;
+    expect(test.call).toThrow();
+  });
+  it("accepts a supplier-invoice blob on a still-collected customer item", () => {
+    const test = setup({ order_item_details: { invoice: { number: "SUP1" } } });
+    test.call();
+    expect(test.next).toHaveBeenCalledOnce();
+  });
+  it("refuses a stock parent changed after the app's check", () => {
+    const test = setup({}, "stock_purchase_items");
+    test.parent.updated = "p2";
+    expect(test.call).toThrow();
+  });
+  it("refuses a stock booking that started after the app's check", () => {
+    const test = setup({}, "stock_purchase_items");
+    test.app.findRecordsByFilter.mockReturnValue([{ id: "new-receipt" }]);
+    expect(test.call).toThrow();
+  });
+  it("allows an unbooked received header to reopen", () => {
+    const test = setup({ status: "received" }, "stock_purchases");
+    test.call();
+    expect(test.next).toHaveBeenCalledOnce();
+  });
+  it("refuses a stock header booked between checking and saving", () => {
+    const test = setup({ status: "received", booked_at: "today" }, "stock_purchases");
+    expect(test.call).toThrow();
+  });
+
+  it("refuses stale confirmation after a reset has committed", () => {
+    const test = setup({ item_status: "collection_pool" });
+    test.info.body = { item_status: "ready_invoice" } as unknown as typeof test.info.body;
+    expect(test.call).toThrow();
+    expect(test.next).not.toHaveBeenCalled();
+  });
+  it("allows normal collection confirmation", () => {
+    const test = setup();
+    test.info.body = { item_status: "ready_invoice" } as unknown as typeof test.info.body;
+    test.call();
+    expect(test.next).toHaveBeenCalledOnce();
+  });
+  it("refuses a stale stock booking ledger insert after a reset reopens the PO", () => {
+    const test = setup({ reference_type: "stock_purchase", reference_id: "po1" });
+    test.parent.status = "sent";
+    expect(test.create).toThrow();
+    expect(test.next).not.toHaveBeenCalled();
+  });
+  it("allows a stock booking ledger insert while the PO is received", () => {
+    const test = setup({ reference_type: "stock_purchase", reference_id: "po1" });
+    test.create();
+    expect(test.next).toHaveBeenCalledOnce();
+  });
+});
diff --git a/src/lib/server/collection-return-service.test.ts b/src/lib/server/collection-return-service.test.ts
new file mode 100644
index 0000000..c082594
--- /dev/null
+++ b/src/lib/server/collection-return-service.test.ts
@@ -0,0 +1,130 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+vi.mock("@/lib/server/pocketbase-admin", () => ({ getAdminPocketBase: vi.fn() }));
+vi.mock("@/lib/server/orders-service", () => ({ getOrderItemsCollectionName: () => "order_items" }));
+
+import { getAdminPocketBase } from "./pocketbase-admin";
+import { returnCollectedToPool } from "./collection-return-service";
+
+const actor = { id: "buyer", name: "Buyer" };
+const customer = { source: "customer" as const, id: "customer1" };
+const stock = { source: "stock" as const, id: "stock1" };
+
+function setup(over: Record<string, unknown> = {}, head: Record<string, unknown> = {}) {
+  const patches: Array<{ collection: string; id: string; patch: Record<string, unknown> }> = [];
+  const send = vi.fn().mockResolvedValue([]);
+  const ledger = vi.fn().mockResolvedValue({ totalItems: 0, items: [] });
+  const pb = {
+    send: vi.fn().mockResolvedValue({ version: 1 }),
+    collection: vi.fn((name: string) => ({
+      getOne: vi.fn().mockResolvedValue(name === "stock_purchases"
+        ? { id: "purchase1", status: "sent", updated: "version1", ...head }
+        : { id: name === "order_items" ? customer.id : stock.id, updated: "version1", item_status: "collected", status: "collected", purchase: "purchase1", drv_id: "driver", qty_collected: 105, quantity_received: 105, quantity: 100, ...over }),
+      getList: ledger,
+    })),
+    filter: (filter: string) => filter,
+    createBatch: () => ({
+      collection: (name: string) => ({ update: (id: string, patch: Record<string, unknown>) => patches.push({ collection: name, id, patch }) }),
+      send,
+    }),
+  };
+  vi.mocked(getAdminPocketBase).mockResolvedValue(pb as never);
+  return { patches, send, ledger, capability: pb.send };
+}
+
+beforeEach(() => vi.clearAllMocks());
+
+describe("returnCollectedToPool", () => {
+  it("resets customer collection and assignment without changing the order or deleting photos", async () => {
+    const { patches, send } = setup();
+    const result = await returnCollectedToPool([customer], actor);
+    expect(result.returned).toEqual([customer]);
+    expect(patches[0]).toMatchObject({ collection: "order_items", id: customer.id, patch: {
+      item_status: "collection_pool", drv_status: "unassigned", drv_id: "", assigned_at: "", drv_assigned_at: "", drv_collected_at: "",
+      qty_assigned: 0, qty_collected: 0, qty_processed: 0, qty_verified: 0,
+      collection_date: "", collected_date: "", ai_check: null, ready_for_collection: true,
+      problem_flag: false, problem_notes: "", problem_type: "",
+    } });
+    for (const key of ["quantity", "order_qty", "purchase_order", "order", "sku", "cost_price", "order_item_attachements", "notes"]) {
+      expect(patches[0].patch).not.toHaveProperty(key);
+    }
+    expect(send).toHaveBeenCalledOnce();
+  });
+
+  it("returns a stock line and reopens an unbooked received stock PO in the same batch", async () => {
+    const { patches } = setup({}, { status: "received" });
+    await returnCollectedToPool([stock], actor);
+    expect(patches).toEqual(expect.arrayContaining([
+      { collection: "stock_purchase_items", id: stock.id, patch: expect.objectContaining({ status: "collection_pool", quantity_received: 0, drv_id: "", assigned_at: "", ai_check: null }) },
+      { collection: "stock_purchases", id: "purchase1", patch: expect.objectContaining({ status: "sent" }) },
+    ]));
+  });
+
+  it.each([
+    { item_status: "invoiced" }, { item_status: "delivered" }, { item_status: "ready_invoice" },
+    { qty_invoiced: 1 }, { qty_delivered: 1 }, { qty_stocked: 1 }, { surplus_qty: 5 },
+    { customer_invoice_number: "INV1" }, { delivery_note_number: "DN1" },
+    { order_item_details: { invoice: { number: "INV1", qbInvoiceId: "q1" } } },
+    { order_item_details: JSON.stringify({ invoice: { number: "INV1", billingCompany: "CNL" } }) },
+  ])("refuses a customer row that has moved on: %j", async (over) => {
+    const { patches, send } = setup(over);
+    const result = await returnCollectedToPool([customer], actor);
+    expect(result.returned).toEqual([]);
+    expect(result.skipped).toHaveLength(1);
+    expect(patches).toEqual([]);
+    expect(send).not.toHaveBeenCalled();
+  });
+
+  it.each([{ status: "booked" }, { status: "assigned_to_driver" }])("refuses stock not collected: %j", async (over) => {
+    const { patches } = setup(over);
+    expect((await returnCollectedToPool([stock], actor)).skipped).toHaveLength(1);
+    expect(patches).toEqual([]);
+  });
+
+  it.each([{ booked_at: "2026-10-21" }, { status: "cancelled" }])("refuses a booked or cancelled stock PO: %j", async (head) => {
+    const { patches } = setup({}, head);
+    expect((await returnCollectedToPool([stock], actor)).skipped).toHaveLength(1);
+    expect(patches).toEqual([]);
+  });
+
+  it("refuses rows with stock-ledger entries even if their status is stale", async () => {
+    const { ledger, patches } = setup();
+    ledger.mockResolvedValue({ totalItems: 1, items: [{ id: "receipt" }] });
+    expect((await returnCollectedToPool([customer, stock], actor)).skipped).toHaveLength(2);
+    expect(patches).toEqual([]);
+  });
+
+  it("deduplicates rows and reports refused rows alongside the returned ones", async () => {
+    const { patches } = setup({ item_status: "invoiced" });
+    const result = await returnCollectedToPool([customer, stock, stock], actor);
+    expect(result.returned).toEqual([stock]);
+    expect(result.skipped).toEqual([expect.objectContaining(customer)]);
+    expect(patches.filter(p => p.collection === "stock_purchase_items")).toHaveLength(1);
+  });
+
+  it("does not report success if the atomic batch fails", async () => {
+    const { send } = setup();
+    send.mockRejectedValue(new Error("batch failed"));
+    await expect(returnCollectedToPool([customer, stock], actor)).rejects.toThrow("batch failed");
+  });
+
+  it("reports a transaction guard refusal as a refreshable conflict", async () => {
+    const { send } = setup();
+    send.mockRejectedValue(Object.assign(new Error("Batch transaction failed"), { status: 400 }));
+    await expect(returnCollectedToPool([customer], actor)).rejects.toMatchObject({ status: 409, message: expect.stringContaining("No items were returned") });
+  });
+
+  it("fails closed without the deployed transaction guard", async () => {
+    const { capability, send } = setup();
+    capability.mockRejectedValue(Object.assign(new Error("Not found"), { status: 404 }));
+    await expect(returnCollectedToPool([customer], actor)).rejects.toMatchObject({ status: 503 });
+    expect(send).not.toHaveBeenCalled();
+  });
+
+  it("sends the checked row revision to the transaction guard", async () => {
+    const { patches } = setup();
+    await returnCollectedToPool([customer, stock], actor);
+    expect(patches[0].patch._collection_return_guard).toEqual({ updated: "version1" });
+    expect(patches[1].patch._collection_return_guard).toEqual({ updated: "version1", parent_updated: "version1" });
+  });
+});
diff --git a/src/lib/server/collection-return-service.ts b/src/lib/server/collection-return-service.ts
new file mode 100644
index 0000000..7c5f581
--- /dev/null
+++ b/src/lib/server/collection-return-service.ts
@@ -0,0 +1,122 @@
+import { getAdminPocketBase } from "./pocketbase-admin";
+import { getOrderItemsCollectionName } from "./orders-service";
+import { runWithAuditActor, type AuditActor } from "./audit-context";
+import { readItemInvoiceNumber } from "@/lib/order-invoices";
+
+export type CollectionReturnRow = { id: string; source: "customer" | "stock" };
+export type CollectionReturnResult = {
+  returned: CollectionReturnRow[];
+  skipped: Array<CollectionReturnRow & { reason: string }>;
+};
+
+/** Return only the collected rows explicitly selected on Collection Confirm.
+ * Keep order quantities, pricing, photos and notes. PB hooks record the changes.
+ * The batch makes line resets and reopening any stock header all-or-nothing.
+ */
+export async function returnCollectedToPool(
+  rows: CollectionReturnRow[],
+  actor: AuditActor,
+): Promise<CollectionReturnResult> {
+  if (!Array.isArray(rows) || rows.length === 0 || rows.length > 500 || rows.some(r =>
+    !r || typeof r.id !== "string" || !r.id.trim() || !["customer", "stock"].includes(r.source),
+  )) {
+    throw Object.assign(new Error("Choose between 1 and 500 collected items."), { status: 400 });
+  }
+  return runWithAuditActor({ ...actor, source: "web" }, async () => {
+    const pb = await getAdminPocketBase();
+    // Unknown PB fields are silently dropped. Never send the guarded batch
+    // unless the hook that enforces its revision checks is actually deployed.
+    try {
+      const capability = await pb.send<{ version: number }>("/api/wfdash/collection-return-guard", { method: "GET" });
+      if (capability.version !== 1) throw new Error("Unsupported guard version");
+    } catch {
+      throw Object.assign(new Error("Return to pool is not available until the PocketBase collection-return guard is deployed."), { status: 503 });
+    }
+    const batch = pb.createBatch();
+    const result: CollectionReturnResult = { returned: [], skipped: [] };
+    const seen = new Set<string>();
+    const reopen = new Map<string, string>();
+
+    for (const row of rows) {
+      const key = `${row.source}:${row.id}`;
+      if (seen.has(key)) continue;
+      seen.add(key);
+      const collection = row.source === "stock" ? "stock_purchase_items" : getOrderItemsCollectionName();
+      let current;
+      try {
+        current = await pb.collection(collection).getOne(row.id);
+      } catch (err) {
+        if ((err as { status?: number }).status !== 404) throw err;
+        result.skipped.push({ ...row, reason: "Item no longer exists." });
+        continue;
+      }
+      const refuse = (reason: string) => result.skipped.push({ ...row, reason });
+      const status = row.source === "stock" ? current.status : current.item_status;
+      if (status !== "collected") {
+        refuse(`Item is ${status || "no longer collected"}; refresh before trying again.`);
+        continue;
+      }
+
+      let purchase;
+      if (row.source === "customer") {
+        const advancedQty = ["qty_invoiced", "qty_delivered", "qty_stocked", "qty_picked", "qty_loaded", "surplus_qty"]
+          .some(field => Number(current[field] ?? 0) > 0);
+        if (advancedQty || readItemInvoiceNumber(current) || current.delivery_note_number || current.invoiced_date || current.delivered_at || current.stock_booked_from) {
+          refuse("Item has already been invoiced, dispatched or booked into stock.");
+          continue;
+        }
+      } else {
+        if (!current.purchase) {
+          refuse("Stock item has no purchase order.");
+          continue;
+        }
+        purchase = await pb.collection("stock_purchases").getOne(current.purchase);
+        if (purchase.booked_at || !["sent", "received"].includes(purchase.status)) {
+          refuse("Stock purchase is already booked or is no longer open for collection.");
+          continue;
+        }
+      }
+
+      // Ledger entries survive some interrupted bookings; do not trust status alone.
+      const ledger = await pb.collection("stock_ledger").getList(1, 1, {
+        filter: pb.filter("reference_type = {:type} && reference_id = {:id}", {
+          type: row.source === "stock" ? "stock_purchase" : "order_item",
+          id: row.source === "stock" ? current.purchase : current.id,
+        }),
+        fields: "id", requestKey: null,
+      });
+      if (ledger.totalItems > 0) {
+        refuse("A stock booking already exists; collection cannot be reset.");
+        continue;
+      }
+
+      const common = {
+        drv_id: "", assigned_at: "", problem_flag: false, problem_type: "", problem_notes: "", ai_check: null,
+        _collection_return_guard: { updated: current.updated, ...(purchase ? { parent_updated: purchase.updated } : {}) },
+      };
+      batch.collection(collection).update(row.id, row.source === "stock" ? {
+        ...common, status: "collection_pool", quantity_received: 0,
+      } : {
+        ...common, item_status: "collection_pool", drv_status: "unassigned",
+        drv_assigned_at: "", drv_collected_at: "", collection_date: "", collected_date: "",
+        qty_assigned: 0, qty_collected: 0, qty_processed: 0, qty_verified: 0,
+        qty_picked: 0, qty_loaded: 0, qty_stocked: 0, qty_delivered: 0, qty_invoiced: 0,
+        verified_date: "", ready_for_collection: true, pool_entered_at: new Date().toISOString(),
+      });
+      if (purchase?.status === "received") reopen.set(purchase.id, purchase.updated);
+      result.returned.push(row);
+    }
+    for (const [id, updated] of reopen) batch.collection("stock_purchases").update(id, { status: "sent", _collection_return_guard: { updated } });
+    if (result.returned.length) {
+      try {
+        await batch.send();
+      } catch (err) {
+        if ((err as { status?: number }).status === 400) {
+          throw Object.assign(new Error("The reset could not be saved; an item may have changed or moved on. No items were returned. Refresh and try again."), { status: 409 });
+        }
+        throw err;
+      }
+    }
+    return result;
+  });
+}