Free tool
Invoice series checker
Gaps and repeated numbers in an invoice series are what GSTR-1 and a GST audit catch. Paste the invoice number column from your sales register and see every gap, repeat and over-long number at once.
Paste the invoice number column from your sales register or GSTR-1 export, one number a line. Up to 20,000 numbers.
Result
3 things to sort out before you file GSTR-1
Missing numbers are fine only if those invoices were cancelled. Report them as cancelled in Table 13 of GSTR-1.
- Numbers checked
- 10
- Series found
- 3
- Missing numbers
- 1
- Repeated numbers
- 1
- Numbers that break Rule 46
- 1
A missing number is only a problem if no invoice was cancelled under it. Repeated numbers must be corrected, because each number must be unique in the financial year.
For GSTR-1 Table 13, documents issued
INV/26-27/0001 to INV/26-27/0007
7 in the range · 1 cancelled or missing · 6 issued
Missing: INV/26-27/0004
EXP/26-27/001 to EXP/26-27/002
2 in the range · 0 cancelled or missing · 2 issued
INV/2026-27/00008 to INV/2026-27/00008
1 in the range · 0 cancelled or missing · 1 issued
Repeated: INV/26-27/0006 and INV/26-27/0006
Over 16 characters: INV/2026-27/00008
Next step in MatruOS
MatruOS continues INV/26-27/ from INV/26-27/0008, one series per branch or GSTIN, so every new invoice runs in order with no repeats.
Let MatruOS number your invoicesKeep this result
Method
How this is worked out
Every figure the tool uses is listed here. Assumptions are fields in the tool, so you can change them to match your business.
- Each number is split into a series (everything before the running number) and the running number at the end.
- Within each series, every number between the first and the last that is missing is listed. Numbers are counted as repeats when the series and the running number match, ignoring capitals and leading zeros.
- Each number is checked against Rule 46(b): up to 16 characters, using letters, digits, hyphen or slash.
- The from, to, total and missing counts per series are the figures GSTR-1 Table 13 asks for. Missing numbers should be the invoices you cancelled.
Questions
Questions people ask
Can I start a new series each financial year?
Yes. The number must be unique for a financial year, so many businesses put the year in the series, such as INV/26-27/0001.
Is a gap in the series wrong?
Not if the invoice was cancelled. Report cancelled numbers in Table 13 of GSTR-1. A gap with no cancelled invoice behind it is a question an officer will ask.
Can I run more than one series?
Yes. Rule 46 allows one or more series, such as one per branch or one for exports. The checker reads each series on its own.
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