Guide · Invoice numbering
Give every invoice one stable identity.
A numbering system should make an invoice easy to find, hard to confuse with another document, and simple enough to continue next month.
Make uniqueness the first rule
Each issued invoice should have one identifier that is not reused for another invoice. A sequence is easier to audit than a random label because you can see what came before and what should come next. Requirements for gaps, cancellations, prefixes, and fiscal years vary by jurisdiction, so confirm the rules that apply to your records before adopting a format.
Pick one format you can keep using
| Pattern | Example | Useful when |
|---|---|---|
| Continuous | INV-00427 | One simple sequence covers the business. |
| Year + sequence | 2026-00427 | The year helps staff browse records. |
| Series + sequence | CONS-00427 | Separate valid series are intentionally maintained. |
Pad the numeric part if it improves sorting: INV-0008 remains beside INV-0009 and before INV-0010. Do not encode a customer email address, phone number, tax identifier, or other private data merely to make the number memorable.
Do not silently recycle a number
When an issued invoice is wrong, preserve the original record and follow the correction method required for your situation. Depending on local practice that may mean a cancellation record, credit note, or a replacement with a new number. Editing a downloaded PDF in place can leave the seller and customer holding different versions under the same identity.
Treat the browser draft as a convenience, not the ledger
Mallow Invoice can save selected drafts in the current browser profile and can export a backup. Those local records do not sync, assign numbers across devices, or replace accounting records. Check the next number against your own source of truth before issuing the invoice, especially when more than one person or device creates them.
Before pressing download
Confirm that the number is unique, the issue date matches the sequence you use, and the PDF shows the same number as your record.