An audit or a tax review is stressful enough without also having to reconstruct which receipt belongs to which sale from memory. A simple, consistent numbering system turns that process from a scramble into a quick lookup.
Sequential numbers, no gaps
Start at 0001 and increment for every receipt issued, in order, with no skipped numbers. A gap in the sequence is exactly the kind of thing that draws extra scrutiny during a review, even when there's an innocent explanation.
Add a year prefix once volume grows
A format like 2026-0001 makes it immediately clear when a receipt was issued and resets cleanly each year, which matters once you're issuing hundreds rather than dozens annually.
Never reuse a number, even for voided transactions
If a sale is cancelled or refunded, mark that receipt number as voided rather than reassigning it — an auditor seeing a clean, gapless sequence with clearly marked voids reads as far more trustworthy than one with silent gaps.
Match the number across every related document
If a sale involved a quote and an invoice before the receipt, referencing the same underlying reference number across all three makes the whole transaction traceable from start to finish in seconds.
Keep a running log, not just the printed slips
A simple spreadsheet listing receipt number, date, amount, and customer is far faster to search during an audit than flipping through a box of paper slips looking for one specific transaction.