diff --git a/src/lib/pdf/purchase-order-document.tsx b/src/lib/pdf/purchase-order-document.tsx
index bbeeb6d..fa6be64 100644
--- a/src/lib/pdf/purchase-order-document.tsx
+++ b/src/lib/pdf/purchase-order-document.tsx
@@ -50,6 +50,13 @@ export interface PurchaseOrderDocumentProps {
  *       Right: PO No / Date / Order Ref
  *   - items table with accent-coloured header (Description / Qty / Unit Cost / Line Total)
  *   - right-aligned totals (rule above Total)
+ *   - **VAT (15%) included** — subtotal + VAT (15%) + rule +
+ *     VAT-inclusive Total, same shape as the quote's totals
+ *     block so the two PDFs feel like siblings. The printed
+ *     `Total` is `subtotal × 1.15` — the figure the office uses
+ *     for budget / VAT-return reconciliation. The stored
+ *     `purchase_orders.total_amount` stays VAT-ex (no PB schema
+ *     change).
  *
  * Intentionally stripped from this document (vs. the quote PDF):
  *   - **No banking details** — supplier invoices via the normal
@@ -60,13 +67,6 @@ export interface PurchaseOrderDocumentProps {
  *     The customer's identity stays internal.
  *   - **No footer text** — keeps the document visually quiet and
  *     prevents accidental leakage of branch-specific marketing copy.
- *   - **VAT (15%) added to subtotal** — prints the supplier-quoted
- *     subtotal, then VAT (15%), then a VAT-inclusive Total. Same
- *     shape as the quote's totals block so the two documents feel
- *     like siblings. The VAT-inclusive Total is the figure the
- *     office uses for budget / VAT-return reconciliation; the stored
- *     `purchase_orders.total_amount` stays VAT-ex (no PB schema
- *     change).
  *
  * Description column uses `po_description` (supplier-facing copy),
  * NOT `description` (internal/operator copy). Falling back to
@@ -91,11 +91,11 @@ export function PurchaseOrderDocument({
       (letterhead.display_name?.toUpperCase().includes("CNL") ? "CNL" : "ISHERWOOD")
     );
 
-  // Subtotal = sum of (qty × cost) per line, using the
-  // `order_qty ?? quantity` supplier-facing fallback. Logic lives
-  // in `poSubtotal()` (src/lib/pdf/format.ts) so it's independently
-  // testable. This keeps the printed line totals summing exactly to the
-  // Subtotal.
+  // Subtotal = sum of effective-qty × cost per line. The "effective
+  // qty" fallback logic (order_qty || quantity, so a literal 0
+  // falls through) lives in `poSubtotal()` (src/lib/pdf/format.ts)
+  // so it's independently testable. The printed line totals sum
+  // exactly to this Subtotal.
   const subtotal = poSubtotal(items);
   // 15% VAT on top of the supplier-quoted subtotal — same helper the
   // quote PDF uses, so both documents compute VAT identically. Total