Invoice Number Series Generator
GST Rule 46(b) requires every tax invoice to carry a consecutive serial number, unique for a financial year, of up to 16 characters, containing only letters, numerals, "/" and "-". Gaps, duplicates or mid-year format changes invite notices and complicate GSTR-1 reconciliation. This generator builds a clean series for you, checks the GST limits, and remembers the last number issued so the next batch continues without overlap.
Build your format
- Prefix — INV, BILL, NC, SRV, a branch code, etc.
- Financial-year part — auto-derived from any date: 25-26, 2025-26, 2025-2026 or FY25-26, or none.
- Separator — slash, hyphen, underscore or none.
- Optional suffix — branch/location such as JPR or SKR.
- Start number, padding (001 / 0001 / 00001), count and increment.
Worked example
Prefix INV, FY short, slash, start 1, padding 4, count 20 → INV/25-26/0001 … INV/25-26/0020 (14 characters ✓). Copy the list, download as CSV with blank Date/Party/Amount columns for a manual invoice register, or feed it into your billing template.
Next-number memory
Click "Mark these as issued" after generating a batch; the tool stores the last number for that exact series (prefix + FY + suffix) in your browser. Next time it warns if your start number would duplicate an issued one and offers "Continue from next". Each financial year automatically becomes a fresh series, as the law requires.
Compliance checks built in
- Length over 16 characters is flagged.
- Characters other than A–Z, 0–9, "/" and "-" are flagged (e.g. underscore or space is not allowed on a GST tax invoice).
- Separate series for credit notes, debit notes, bills of supply and branches are permitted — just change the prefix.
Good practice
Keep one series per document type per FY, never reuse a cancelled number (issue a credit note instead), and restart from 0001 on 1 April. Declare the series ranges in GSTR-1 Table 13 (documents issued).
Frequently Asked Questions
Can an invoice number contain a space or underscore?
No. Rule 46 permits only alphabets, numerals, slash and hyphen. The tool warns if you choose an underscore separator.
Must I restart numbering every financial year?
Yes — the serial must be unique within a financial year; most businesses restart at 1 on 1 April with the FY in the prefix.
Can I run multiple series at once?
Yes, e.g. INV/25-26/ for sales and CN/25-26/ for credit notes, or per branch. Each series must itself be consecutive.
Where is the "next number" stored?
In your browser's localStorage, per series key. Clearing browser data resets it.
Disclaimer: This tool is for general information and estimation only. Tax rates and rules change — verify with official sources or a professional before acting. Read full disclaimer.