How do I cancel an approved invoice, and what exactly gets reversed?

Cancelling is not deleting. The invoice stays in the list as cancelled, and everything approval posted is reversed — nothing is left half-done.

Steps

1. Open the invoice from Sales → Sales Invoices — image 1.
2. Press Cancel.
3. Confirm the warning: "Are you sure? This will reverse the journal entries." For a POS invoice the warning is broader, because it covers the receipt and the stock as well.

What gets reversed

• The journal entry — a reversing entry undoes the revenue, the receivable and the tax.
• Stock — the quantities return to the warehouse they left.
• The receipt — on a POS invoice every linked receipt is deleted, including all legs of a split payment, not just the first.
• The invoice status — becomes cancelled, and it can never again be edited, reopened, or take a payment.

When the system refuses

• It has a sales return. The return already gave part of the goods back, so cancelling afterwards would double-credit the returned portion. Delete the return first.
• A POS invoice whose shift is closed. That shift's cash has been counted and reconciled, so it cannot be changed retroactively.
• A POS invoice without the permission. Cancelling one is a separate permission from cancelling ordinary invoices.
• The invoice is a draft. Cancelling means nothing — delete it.

Notes

• Cancellation is protected against concurrency; two simultaneous requests never reverse the entry twice or return the stock twice.
• Bulk cancel from the list runs the same logic and never skips the reversal.
• If the mistake is one line's quantity or price, a return is more precise than a cancellation; cancelling is for the whole deal.
• Check the activity log afterwards to record who cancelled and when.
• Numbers are never reused; a cancelled invoice keeps its number for itself, and that is deliberate.