A cashier voids a bill. Ten minutes later someone asks the question every shop eventually asks: can we use that invoice number again? The answer decides whether your books and your GST return tell the same story, so it is worth getting right once and settling it.
What the rule actually asks for
Rule 46 of the CGST Rules describes what a tax invoice must carry. For the serial number, the requirements come down to four things:
- A consecutive serial number, not more than sixteen characters.
- It may contain letters, numbers, and the symbols "-" and "/". So INV/2026-27/001 is a perfectly legal shape.
- It must be unique for a financial year. One serial, one document, one year.
- You may run one or several series. A counter series and a wholesale series side by side is allowed, as long as each stays consistent.
Notice what the rule does not say. It does not say numbers may never restart: they restart every April, because uniqueness is scoped to the financial year. And it does not spell out the word "cancelled" at all, which is why the question keeps coming up.
Why a cancelled number stays used
A cancelled invoice was still issued. It existed, it may have been printed, and the customer may be holding a copy. GSTR-1 has a section for exactly this: Table 13, "Documents issued", where you report the serial ranges you used in the period, the total count, and how many of those were cancelled.
That reporting is what closes the door on reuse. If bill number 103 is reported as issued and cancelled, and a second bill also carries number 103 in the same year, you now have two documents on one serial: one your return calls cancelled, one your customer calls their purchase. Any mismatch check between your books and your return will trip over it, and you cannot fix it after the return is filed.
Made a mistake on a bill? Use a credit note, not the same number
If goods come back, or a bill was made for the wrong amount, the fix is not to re-issue the invoice under the same number. Section 34 gives you the credit note: a separate document, with its own number, issued against the original invoice. The original keeps its serial, the credit note reverses the value, and both appear in your return doing their own jobs.
Are gaps in the series a problem?
Real shops get gaps. A test bill deleted on day one, a numbering series changed mid-year, an entry removed because it should never have existed. Table 13 is built to describe reality: you report the documents that exist, as ranges, with the cancelled count alongside.
A gap is not an offence by itself. What matters is that you can explain it. An officer looking at your return can see that number 57 is missing and may ask what happened to it, and "our software recorded the deletion on this date, here is the log" is a complete answer. Silence is not.
The part software should do for you
None of this should depend on a cashier remembering rules during a rush. This is how Layerdots ERP handles it, and the behaviour is worth demanding from any billing software:
- Cancel keeps the number. A cancelled bill stays in the books, marked cancelled, holding its serial. The app refuses to give that number to any other bill and says why, instead of failing with a vague error.
- Delete is a separate, deliberate act for bills that should never have existed: a test entry, a duplicate. The bill moves to a recycle bin for 30 days, the deletion is written to the activity log with the user's name, and the number becomes available again. Whether to leave a gap or refill it stays your choice.
- Documents issued is prepared for you. The GSTR-1 export reports the ranges that actually exist, with cancelled documents counted, rather than pretending the series was unbroken.
- Two devices cannot collide. If the phone app also makes bills, both devices draw from one shared series, so the same number can never be issued twice, even in the same second.
Common questions
Can a cancelled invoice's number be used again?
Not in the same financial year. The cancelled invoice is reported as an issued, cancelled document,
and a second bill on the same serial would contradict that. After April, the new year's series can
use the number again.
Can I restart from number 1 every April?
Yes. Uniqueness is per financial year. Most shops restart with a year marker in the series, like
2026-27/001, so old and new bills can never be confused.
Is a gap in invoice numbers illegal?
No, but expect to explain it. Keep a record of why the number is missing. Software that logs
deletions gives you that answer for free.
My software reused a cancelled number by itself. Is that a problem?
It can be, if both documents fall in the same financial year and both were reported. Check what
your return declared for that period, and change the setting or the software so it does not happen
again.
This article is general information for shop owners, not legal advice. For a dispute or a notice, speak to your CA or a GST practitioner.