How Invoice Numbering Resets Each Financial Year (and Why Gaps Are Illegal)
Rule 46(b) covers what a compliant invoice number has to look like structurally. This is about the part that trips people up operationally: the reset itself.
The rule
Invoice numbers must be consecutive and unique within a financial year, per series. That means on 1 April, your numbering starts fresh — invoice 1 of the new financial year, not a continuation of last year's count. Carrying last year's number forward, or restarting mid-year without a documented reason, both break compliance.
Why this catches businesses out
- Software that doesn't know what a financial year boundary is — a plain auto-increment counter with no year-awareness either never resets (wrong) or resets on the calendar year instead of April 1 (also wrong).
- A late invoice from the old year, entered after the reset — this needs to go into the correct year's sequence based on its actual invoice date, not the date it happened to be entered.
- Multiple series active at once — each series resets independently; see managing multiple invoice series if you run more than one.
What "gap-free" actually means in an audit
If your GSTR-1 shows invoices 1, 2, 3, 5 for a financial year, invoice 4 is either missing (a real compliance issue) or was voided without a proper record. A cancelled invoice's number should still be accounted for, not silently skipped — the number stays reserved even if the invoice itself is cancelled, so the sequence has no unexplained hole in it.
This is exactly the kind of thing that should be enforced structurally rather than tracked by memory — a numbering scheme that can't produce a duplicate or a silent gap, by construction, regardless of who's issuing invoices or how many people have access.