Built by Pyalm
Pyalm Books raises tax invoices, credit notes and receipts from one sales cycle instead of a hand-numbered spreadsheet, so there are fewer places for a numbering gap to appear.
Paste a list of document numbers. The tool separates series by prefix, then reports every missing number, compressed into ranges, and any number that appears more than once.
Paste invoice, credit note, voucher or cheque numbers — one per line, or separated by commas. Mixed series are analysed separately.
Pyalm Books raises tax invoices, credit notes and receipts from one sales cycle instead of a hand-numbered spreadsheet, so there are fewer places for a numbering gap to appear.
Tax invoices are expected to carry a unique, sequential number. A gap may be a voided draft or a cancelled document, but unexplained gaps suggest invoices issued outside the books or deleted after the fact. Auditors routinely test completeness by checking sequences, and so can you before they do.
Each entry is split into a prefix and a trailing number, so INV-2026-0101 and CN-2026-0007 become two separate series. Numbers are sorted, duplicates removed and reported, and gaps are listed as ranges (INV-2026-0107 → INV-2026-0109). Leading zeros are preserved in the output. Entries with no trailing number are listed as ignored.
📖 Read the full guide: Missing Invoice Numbers: Testing Sequence Gaps
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Not by itself. What matters is that every number is accounted for — a voided or cancelled document should be retained and marked, not silently deleted. Check your tax authority's rules for numbering and voided documents.
Yes. A list of tens of thousands analyses instantly in your browser. Very large gaps are shown as ranges rather than listed number by number.
If the year is part of the prefix (INV-2026-…), each year forms its own series automatically.
