Why Invoice Numbers Must Be Sequential.
Why tax authorities require sequential invoice numbers, what happens when you skip a number, and how InvoiceScript handles numbering.
Why Invoice Numbers Must Be Sequential
For: business owners and bookkeepers who need to understand the rules around invoice numbering.
The rule
Most tax authorities require invoice numbers to be sequential and unique. The reason is auditability: if your invoices go 001, 002, 004, someone will ask what happened to 003. A gap suggests a missing invoice, which suggests unreported income.
The specific rules vary by country. Some require strict sequential ordering (the Netherlands, Germany). Others allow gaps but require uniqueness (the UK). In all cases, the number must be assigned once, printed on the document, and never changed.
How InvoiceScript handles it
InvoiceScript assigns document numbers at finalization, not at draft creation. While an invoice is a draft, it has a temporary code (like DRAFT-A3F2K9) and no permanent number. This prevents gaps from deleted drafts.
When you click Finalize:
- InvoiceScript reads the current counter from your numbering sequence.
- It formats the number using your configured pattern (for example, NW-2026-0003).
- It writes the number to the invoice record.
- It advances the counter.
The number is immutable from this point. You cannot change it, and you cannot reassign it to another document.
What about cancelled invoices?
Cancelling an invoice does not free its number. Invoice NW-2026-0003 stays NW-2026-0003 even after cancellation. The next invoice gets NW-2026-0004. Your audit trail shows a cancelled invoice at position 3, which is a legitimate business event.
If your accountant asks "what happened to NW-2026-0003?", the answer is in the system: it was cancelled on a specific date, by a specific user, and an audit log entry records the event.
Worked example
Mira Holst at Northwind Studio creates three invoices this month:
- NW-2026-0001, sent and paid
- NW-2026-0002, cancelled (customer backed out before delivery)
- NW-2026-0003, sent, awaiting payment
Her accountant sees all three in sequence. The cancelled invoice is marked as cancelled with its original totals preserved. No gap, no questions.
Counter overrides
InvoiceScript lets you override the counter at finalization time. If you are migrating from another system and need your next invoice to be NW-2026-0248, set the counter to 248 in Settings or override it on the finalization screen.
The system always advances past the assigned number, even with overrides. If you override to 250, the next automatic counter becomes 251.
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