GST Invoice Number Rules: Length, Series, New Financial Year and Cancelled Bills

What the rule says

Rule 46(b) of the CGST Rules says a tax invoice must carry "a consecutive serial number not exceeding sixteen characters, in one or multiple series", using letters, numbers, hyphen (-) and slash (/), and "unique for a financial year". The same wording applies to a bill of supply (Rule 49) and to credit and debit notes (Rule 53). A delivery challan (Rule 55) must also be serially numbered, up to 16 characters.

• Up to 16 characters in total, counting the prefix, year, separators and digits.
• Allowed characters: letters A–Z, digits 0–9, hyphen (-) and slash (/). No spaces, dots, # or other symbols.
• Consecutive: each new bill takes the next number. Do not skip numbers or go back to an old one.
• Unique for the financial year: the same number must not appear twice between 1 April and 31 March.
• One or multiple series: you may run more than one series, as long as each series follows these rules.

Good and bad invoice number formats

Scroll sideways to see all columns.

Count the characters of your longest number of the year (for example bill 10000 if you make many bills) before you fix a format.

Separate series for branches and document types

Because the rule allows "one or multiple series", a business may keep separate series, for example one per shop counter or branch, or a separate series for exports. Each series must still be consecutive and unique for the year, and the prefix should make it clear which series a number belongs to (for example A/26-27/1 and B/26-27/1). A branch in another state has its own GSTIN and keeps its own series.

Starting a new series every financial year

Since numbers must be unique for a financial year, the usual practice is to start a fresh series on 1 April, with the year in the number (for example 26-27). GSTN issued an advisory on 4 April 2019 asking taxpayers to start a new invoice series, unique for the financial year, from 1 April, and warned that not doing so can cause problems in e-way bills, GSTR-1 and refunds.

You may restart at 1 each year, because the year in the number keeps INV/25-26/1 and INV/26-27/1 different.

Cancelled bills: do not delete or reuse the number

• If a bill is cancelled before the goods go out, keep it in your books marked cancelled. Do not delete it and do not give its number to another bill, otherwise your series shows a gap or a duplicate.
• In GSTR-1, Table 13 (documents issued) asks for the serial number range of the invoices issued in the period, the total number and how many were cancelled.
• e-Invoice: an IRN can be cancelled on the IRP only within 24 hours, and not if an active e-way bill is linked to it. The number of a cancelled IRN cannot be used again for another e-Invoice.
• If the goods were already supplied, do not cancel the bill. Issue a credit note against it instead (see the credit note and sales return guide).

Credit note and debit note numbers

A credit note needs its own consecutive serial number of up to 16 characters, unique for the financial year, plus the number and date of the original invoice it is issued against. Keep credit notes in their own series (for example CN/26-27/1 for the first one of the year) so the invoice series stays continuous. Debit notes and delivery challans are usually given their own series in the same way.

How BizBahi numbers your bills

• You choose the invoice prefix, starting number and financial year when you set up your business. Later, the prefix and number format can be changed in Settings → Document Options (Invoice).
• Number format options: separator slash (HCE/26-27/1) or dash (HCE-26-27-1), number padding (none, 001, 0001 or 00001) and the year as short (26-27) or long (2026-27). The screen shows a preview of the next bill number, so you can count its length.
• The number is given automatically from the counter when a bill is saved. Editing a bill keeps its number, and saving the settings again never moves the counter backwards.
• New financial year: with the option "New financial year (1 April): switch FY and restart numbering" on (it is on by default), the first bill dated on or after 1 April gets the new year in its number and the count restarts from your starting number.
• Credit notes, debit notes, delivery challans and proforma invoices each have their own series with their own prefix (CN, DN, DC, PF) and restart in the new financial year too.
• Cancelling: Delete (void) in the Sales list does not erase the bill. It stays in the list marked void, and its number is not reused. A bill that already has a credit note cannot be voided.
• In the GSTR-1 export (paid plans and the 7-day trial), the docs sheet lists the invoice number range, total count and the number of voided bills as cancelled, plus the credit note range.
• Before making an e-Invoice JSON, BizBahi checks that the number is 1–16 characters, uses only A–Z, 0–9, / and -, and does not start with 0.

Quick checklist

1. Pick a short prefix (your shop initials, 3–4 letters), the short year (26-27) and / or - as the separator.
2. Check that your longest number of the year stays within 16 characters.
3. Start a new series on 1 April every year.
4. Never delete or reuse a bill number; mark wrong bills as cancelled, or issue a credit note if the goods were supplied.

What is the maximum length of a GST invoice number?

16 characters, including the prefix, year, separators and digits. Only letters, numbers, hyphen (-) and slash (/) are allowed.

Can I restart invoice numbers from 1 in a new financial year?

Yes. The number must be unique only within a financial year, so most businesses start a new series on 1 April and keep the year in the number, for example INV/26-27/1.

Can I use more than one invoice series?

Yes. Rule 46 allows one or multiple series, for example one per branch or counter. Each series must be consecutive and unique for the financial year.

What should I do with a cancelled invoice number?

Keep the bill marked cancelled and do not reuse its number. Report it as cancelled in Table 13 of GSTR-1. If the goods were already supplied, issue a credit note instead of cancelling.

Can an e-Invoice number start with 0?

No. On the IRP the document number must not start with 0, / or -, and lowercase letters are rejected. Use a prefix such as INV.

Does BizBahi restart bill numbers on 1 April?

Yes, by default. The first bill dated in the new financial year gets the new year in its number and the count restarts from your starting number. You can turn this off in Settings → Document Options.