Guides · Invoicing
Invoice numbering rules
Invoice numbering sounds trivial, but under GST it is a rule. A tax invoice number has to run in a consecutive series that is unique for the financial year — and gaps or duplicates are where reconciliation problems start.
What the numbering rule requires
A tax invoice must carry a consecutive serial number, unique within a financial year. The series can use letters, numbers, and some separators, but it has to be continuous — one number following the last, without gaps or repeats.
A business can run more than one series, but each has to stay consistent and unique for the year, so the total set of invoices is still traceable.
Why gaps cause trouble
A missing number raises the obvious question — where did that invoice go? A duplicate number means two supplies share an identity, which breaks matching. Both undermine the trust that the invoice record is complete, which is exactly what a tax officer checks.
Manual books are where gaps creep in: a cancelled bill, a torn page, a parallel pad started mid-year.
How Lekha keeps the series gap-free
Lekha generates GST-compliant delivery challans and tax invoices against a purchase order, with HSN, place of supply, and the right CGST/SGST or IGST split computed live, and gap-free financial-year numbering.
The numbering is kept gap-free per financial year automatically, so the series stays consecutive without anyone tracking the last number by hand.
Questions
- What are the GST invoice numbering rules?
- A tax invoice number must be a consecutive serial, unique within the financial year. It can use letters, numbers, and some separators, but must stay continuous.
- Can I run more than one invoice series?
- Yes, but each series has to stay consistent and unique for the financial year, so all the invoices remain traceable.
- Why do gaps in invoice numbers matter?
- A gap raises the question of a missing invoice and a duplicate breaks matching. Both undermine confidence that the invoice record is complete.
This guide is general information, not legal or tax advice. Confirm the current rules and your own circumstances for any specific case.