Invoice number generator and numbering scheme preview

Unique, sequential, and with no gaps you cannot explain. That is the whole requirement, and it is the one most manual systems fail — usually the first time two invoices go out on the same day and both get the same number.

Padding matters more than it looks. INV-0001 sorts correctly in every file listing and spreadsheet; INV-1 puts invoice 10 before invoice 2 forever. Pick four digits unless you know you will exceed 9,999 documents in a series.

Including the year makes documents easy to find but restarts the sequence annually, which some accountants prefer and others dislike. Either is defensible; changing your mind halfway through a year is not.

VegaPal maintains a separate sequence per document type, so quotations, proforma invoices and tax invoices each run their own series and cannot collide. The next number is assigned when you create a document, which is what keeps the series unbroken without you tracking the last one used.

That separation is deliberate: mixed series across document types are exactly what an auditor asks about, because a proforma sitting in the middle of your tax invoice numbering looks like a missing sale until somebody explains it.