GST invoice number checker
Paste your invoice numbers and see which break the 16-character rule, which are used twice, and which are missing from the series.
6 numbers. Nothing leaves your browser.
A few things to look at:
Not allowed under Rule 46 (2)
- INV/2026-27/KA/0005: 19 characters; the limit is 16.
- INV #6: Not allowed: space, “#”. Use letters, digits, “-” and “/”. Try INV-6.
Used more than once
INV/26-27/0004
Missing from a series
Numbers should run in sequence. A missing one is fine if you cancelled it, but it goes in the cancelled count in the document summary (Table 13).
- INV/26-27/0003
Questions people ask
- How many characters can a GST invoice number have?
- No more than 16. Letters, digits, hyphens and slashes all count.
- Which characters are allowed in a GST invoice number?
- Letters, digits, the hyphen (-) and the slash (/). Spaces, #, _, &, full stops and other symbols are not allowed.
- Can the same invoice number be used twice?
- Not under the same GSTIN in the same financial year. A number must be unique, and each series must run in sequence.
- Do I have to restart numbering every year?
- Yes. Start a fresh series for each financial year. Rule 46 doesn't say what number to begin with.
- My invoice number is longer than 16 characters. What now?
- Shorten it. Writing the year as 26-27 instead of 2026-27 often saves enough. Don't edit invoices you have already issued: change the series from the next invoice.
- Can I use more than one series?
- Yes, for example one per branch or one for credit notes. Each series must be consecutive, and every number must stay unique for the year.
Rules last checked 18 October 2026. This is general information, not tax advice. Check the notification or ask your CA before you rely on a figure.
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