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Invoice number generator · Free

Invoice number generator for GST invoices

Pick a prefix, the financial year and a separator, and see your next invoice numbers, checked against the GST rules as you type.

Invoice number generator

Runs in your browser. Nothing you type is sent or saved.

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The rule in short

Rule 46(b) of the CGST Rules, 2017 says every tax invoice needs a consecutive serial number of at most 16 characters, made of letters, digits, hyphens (-) and slashes (/) only, unique for the financial year. You can run one series or several (for example one per branch), as long as no number repeats within the year.

The rules for an invoice number

  • At most 16 characters in total, counting the prefix, year and separators
  • Only letters, digits, hyphen (-) and slash (/); no spaces, #, * or @
  • Consecutive: each number follows the last one in its series
  • Unique within the financial year (1 April to 31 March)
  • Bills of supply follow the same rule (CGST Rule 49)

A good pattern

A short prefix, the financial year and a running number, such as INV/26-27/0001. Starting a new series each April keeps numbers from clashing across years. Use a different prefix for each branch or type of document (for example QT for quotes and CN for credit notes) so every series stays consecutive.

Why it matters

The invoice number is reported in GSTR-1 and used in e-way bills and e-invoices. A number longer than 16 characters, or one with other symbols, can be rejected by the GST portal.

How to use it

  1. Choose a prefix

    A few letters for the business, branch or document type, like INV or KOC.

  2. Pick the year format and separator

    Short (26-27) or long (2026-27) financial year, joined with - or /.

  3. Set the starting number and digits

    See your next five numbers and a check against the 16-character limit.

Frequently asked questions

How many characters can a GST invoice number have?

At most 16, including any prefix, year and separators (CGST Rules, Rule 46(b)).

Which special characters are allowed?

Only the hyphen (-) and the slash (/). Letters and digits are fine; spaces and other symbols are not.

Must I restart numbering every April?

The rule only needs numbers to be unique within the financial year. Most businesses start a new series each April with the year in the number, which keeps that easy.

Can I use more than one series?

Yes. You can run separate series, for example one per branch or counter, as long as each is consecutive and no number repeats in the year.

Sources

This page explains the rules in general terms as of November 2026. It is not tax or legal advice; check your case with your CA.

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