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InvoicesKitPro

How to Number Your Invoices (With Examples)

By InvoicesKitPro · · 4 min read

Invoice numbers must be unique and usually sequential. Good formats, rules for India GST, and what to do when you make a mistake.

Unique and in sequence

Tax authorities expect each invoice number to be used once and to follow a sequence, so gaps or duplicates can raise questions. A simple counter is enough; you do not need anything clever.

Formats that work

Some common patterns:

  • INV-2026-0001: prefix, year and counter (this generator's default)
  • 2026/27/015: financial year and counter, popular in India
  • QT-2026-0004 or CN-2026-0002: different prefixes for quotes and credit notes

India GST rules

Under GST, an invoice number can have at most 16 characters and may only use letters, numbers, hyphens and slashes. It must be unique for the financial year. The generator warns you if a number breaks these rules.

Fixing mistakes

Do not delete or reuse a number once an invoice has been sent. Issue a credit note against it instead, then a new invoice with the next number. This keeps your records clean if you are ever audited.

Ready to try it?

Start numbered invoices

This guide is general information, not tax or legal advice. Rules change; check with your tax authority or accountant.

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