diff --git a/src/components/collection-confirm/confirm-invoice-dialog.test.tsx b/src/components/collection-confirm/confirm-invoice-dialog.test.tsx
new file mode 100644
index 0000000..14ea609
--- /dev/null
+++ b/src/components/collection-confirm/confirm-invoice-dialog.test.tsx
@@ -0,0 +1,210 @@
+import { render, screen, waitFor, within } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+import { ConfirmInvoiceDialog } from "./confirm-invoice-dialog";
+
+const costOverrides = { "row-1": 50 };
+
+function getDialog() {
+  return screen.getByRole("dialog");
+}
+
+function getDateInput(dialog = getDialog()) {
+  return within(dialog).getByLabelText(/Supplier invoice date/i);
+}
+
+function getNumberInput(dialog = getDialog()) {
+  return within(dialog).getByLabelText(/Supplier invoice number/i);
+}
+
+function getSubmitButton(dialog = getDialog()) {
+  return within(dialog).getByRole("button", { name: /^Confirm(?: \d+ items)?$/i });
+}
+
+afterEach(() => {
+  vi.restoreAllMocks();
+});
+
+describe("ConfirmInvoiceDialog", () => {
+  it("renders the row and cost override summary", () => {
+    render(
+      <ConfirmInvoiceDialog
+        open
+        onOpenChange={vi.fn()}
+        onSubmit={vi.fn()}
+        rowCount={2}
+        costOverrides={costOverrides}
+      />,
+    );
+
+    expect(
+      within(getDialog()).getByText(/Confirming 2 rows/i),
+    ).toHaveTextContent("Confirming 2 rows · 1 cost override applied");
+  });
+
+  it("calls onSubmit with the invoice details and cost overrides", async () => {
+    const user = userEvent.setup();
+    const onSubmit = vi.fn();
+    render(
+      <ConfirmInvoiceDialog
+        open
+        onOpenChange={vi.fn()}
+        onSubmit={onSubmit}
+        defaultValues={{ date: "", number: "" }}
+        costOverrides={costOverrides}
+      />,
+    );
+
+    await user.type(getDateInput(), "2026-08-03");
+    await user.type(getNumberInput(), "INV-001");
+    await user.click(getSubmitButton());
+
+    expect(onSubmit).toHaveBeenCalledTimes(1);
+    expect(onSubmit).toHaveBeenCalledWith({
+      invoice: { date: "2026-08-03", number: "INV-001" },
+      costOverrides,
+    });
+  });
+
+  it("disables submit when the date is empty", async () => {
+    const user = userEvent.setup();
+    render(
+      <ConfirmInvoiceDialog
+        open
+        onOpenChange={vi.fn()}
+        onSubmit={vi.fn()}
+        defaultValues={{ date: "", number: "" }}
+      />,
+    );
+
+    await user.type(getNumberInput(), "INV-001");
+
+    expect(getSubmitButton()).toBeDisabled();
+  });
+
+  it("disables submit when the invoice number is empty", async () => {
+    const user = userEvent.setup();
+    render(
+      <ConfirmInvoiceDialog
+        open
+        onOpenChange={vi.fn()}
+        onSubmit={vi.fn()}
+        defaultValues={{ date: "", number: "" }}
+      />,
+    );
+
+    await user.type(getDateInput(), "2026-08-03");
+
+    expect(getSubmitButton()).toBeDisabled();
+  });
+
+  it("disables submit when both invoice fields are empty", () => {
+    render(
+      <ConfirmInvoiceDialog
+        open
+        onOpenChange={vi.fn()}
+        onSubmit={vi.fn()}
+        defaultValues={{ date: "", number: "" }}
+      />,
+    );
+
+    expect(getSubmitButton()).toBeDisabled();
+  });
+
+  it("trims the invoice number before submitting", async () => {
+    const user = userEvent.setup();
+    const onSubmit = vi.fn();
+    render(
+      <ConfirmInvoiceDialog
+        open
+        onOpenChange={vi.fn()}
+        onSubmit={onSubmit}
+        defaultValues={{ date: "2026-08-03", number: "" }}
+        costOverrides={costOverrides}
+      />,
+    );
+
+    await user.type(getNumberInput(), "  INV-001  ");
+    await user.click(getSubmitButton());
+
+    expect(onSubmit).toHaveBeenCalledTimes(1);
+    expect(onSubmit.mock.calls[0][0].invoice.number).toBe("INV-001");
+  });
+
+  it("uses singular row and plural zero-overrides labels", () => {
+    render(
+      <ConfirmInvoiceDialog
+        open
+        onOpenChange={vi.fn()}
+        onSubmit={vi.fn()}
+        rowCount={1}
+        costOverrides={{}}
+      />,
+    );
+
+    expect(
+      within(getDialog()).getByText(/Confirming 1 row/i),
+    ).toHaveTextContent("Confirming 1 row · 0 cost overrides applied");
+  });
+
+  it("re-applies updated defaults when reopened", async () => {
+    const onOpenChange = vi.fn();
+    const onSubmit = vi.fn();
+    const { rerender } = render(
+      <ConfirmInvoiceDialog
+        open
+        onOpenChange={onOpenChange}
+        onSubmit={onSubmit}
+        defaultValues={{ date: "2026-08-01", number: "INV-OLD" }}
+      />,
+    );
+
+    expect(getDateInput()).toHaveValue("2026-08-01");
+    expect(getNumberInput()).toHaveValue("INV-OLD");
+
+    rerender(
+      <ConfirmInvoiceDialog
+        open={false}
+        onOpenChange={onOpenChange}
+        onSubmit={onSubmit}
+        defaultValues={{ date: "2026-08-01", number: "INV-OLD" }}
+      />,
+    );
+
+    await waitFor(() =>
+      expect(screen.queryByRole("dialog")).not.toBeInTheDocument(),
+    );
+
+    rerender(
+      <ConfirmInvoiceDialog
+        open
+        onOpenChange={onOpenChange}
+        onSubmit={onSubmit}
+        defaultValues={{ date: "2026-08-02", number: "INV-NEW" }}
+      />,
+    );
+
+    const reopenedDialog = await screen.findByRole("dialog");
+    await waitFor(() => {
+      expect(getDateInput(reopenedDialog)).toHaveValue("2026-08-02");
+      expect(getNumberInput(reopenedDialog)).toHaveValue("INV-NEW");
+    });
+  });
+
+  it("closes the dialog when Cancel is clicked", async () => {
+    const user = userEvent.setup();
+    const onOpenChange = vi.fn();
+    render(
+      <ConfirmInvoiceDialog
+        open
+        onOpenChange={onOpenChange}
+        onSubmit={vi.fn()}
+      />,
+    );
+
+    await user.click(within(getDialog()).getByRole("button", { name: /Cancel/i }));
+
+    expect(onOpenChange).toHaveBeenCalledWith(false);
+  });
+});