GST Invoice Numbering Rules – What You Must Follow
GST invoices must be numbered sequentially and uniquely. No gaps, no repeats.
Rules
- Sequential – INV-001, INV-002, INV-003…
- Unique – Each invoice gets one number
- No gaps – Don’t skip numbers (even for cancelled invoices, note as cancelled)
- Financial year – Many businesses restart from 1 each FY (INV/24-25/001)
Format
Common formats:
- Simple: 1, 2, 3…
- With prefix: INV-001, BIL/2024-001
- With FY: INV/24-25/001
Tips
- Use a prefix for different types (INV for sales, PINV for purchase)
- Don’t reuse numbers
- Keep a record; auditors may ask
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