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Invoice numbering

A numbering series is the one thing in an accounting system that an inspector will check without being asked. Gaps and duplicates are both findings. Here is how ours cannot produce either.

One series per document type

Invoices, quotes, credit notes, proformas and delivery notes each have their own series, with their own prefix, their own counter and their own reset rule. Set them in Settings → Numbering. A series looks like INV-{YYYY}-{0000}: the literal part is yours, {YYYY} is the year of the issue date, and the zeros set the width.

Numbers are taken, not guessed

The counter is incremented in the database at the moment of issue, not read and written back by the application. Two people pressing Issue in the same second get two different numbers. This sounds obvious; it is the single most common way invoicing systems produce duplicates.

A failed issue does not burn a number

Everything that can refuse an issue runs before the number is taken: the missing company name, an empty document, and the stock check when you have it switched to blocking. If any of them stops you, the series has not moved. Fix the problem, press Issue again, and you get the number you would have had.

This is why the stock check cannot run after numbering. A document that holds a number has been issued; refusing to move stock at that point would leave an issued invoice with no stock deduction behind it, which is a quiet lie in the ledger. So the order is fixed: check, then number, then move the goods — and if the goods go negative, they go negative visibly.

Yearly reset

Most countries expect the counter to restart each year. Turn that on in the series and the first document of January gets 0001 again, under the new year. The old year's numbers are untouched — they are not re-issued and not reused.

Backdating

You can issue with a past date, and the series follows the issue date, not today. What you cannot do is insert a number between two that already exist. If that is what you need, the honest fix is a credit note and a fresh invoice, in today's order.

Questions people actually ask

What happens to the number if I void an invoice?

It stays with the voided document. A series with a hole in it is a problem at an inspection; a voided invoice that keeps its number and says "void" is not.

Can I run two series at the same time, for two branches?

Yes. Add a second series for the same document type and pick it on the document. Each keeps its own counter.

Can I change the prefix mid-year?

You can, but think about it first. Most tax authorities accept a change of prefix as long as the sequence inside each prefix is unbroken and the change is documented.

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