Numberinginvoicesacrossclientsandbranches
One series is simplest. Several are permitted. What is not permitted is a series that is not consecutive, which is what happens by accident.
5 minute read · Updated
Short answer
GST permits one series or several, provided each is consecutive and unique for the financial year. A single series across all clients is simplest and is right for most small businesses — never number per client, which produces duplicates. Separate series are worth running per state registration, per branch, or per document type, and each then needs its own prefix. Where invoices are raised in two different tools, decide which owns the numbering and let the other follow it, because two systems each incrementing independently will collide.
One series, or several
| Situation | Series |
|---|---|
| One person, many clients | One series across everything |
| Several document types | One per type — INV, QUO, PI, CN |
| Multiple state registrations | One per registration |
| Branches invoicing separately | One per branch, with a branch prefix |
| Per client | Never — it produces duplicates |
The per-client row is the one worth stating explicitly, because it is an intuitive idea and a bad one. Numbering restarted for each client means several invoices numbered 001 in the same financial year, and uniqueness is the requirement.
Keeping several series straight
Where you do run several, the prefix carries the distinction and everything after it stays identical in shape:
- `INV-202608-001` — invoices
- `QUO-202608-001` — quotations
- `PI-202608-001` — proforma
- `CN-202608-001` — credit notes
- `KOL-INV-202608-001` — where a branch needs its own
Each is independently consecutive. They do not interleave and they do not need to. The generator switches the prefix automatically when you change document type, which is what keeps quotations out of your invoice sequence.
Two tools, one series
The common failure: accounting software raises the recurring invoices, a generator raises the one-off quotations and credit notes, and both are incrementing from their own idea of the last number.
- 01Decide which system owns the invoice series. Usually the accounting software, since it raises the most.
- 02Give the other system a different document type or prefix so the two never collide.
- 03Before raising anything manually, check the last number the owning system issued.
- 04Record manual invoices back into the owning system the same week, not at year end.
- 05Reconcile the series once a month — read it top to bottom and look for a gap.
That monthly read is thirty seconds and it is the only reliable way to catch a duplicate while you can still remember the circumstances. A collision discovered at year end is a much longer conversation.
The reference
Invoice number format
What GST requires of an invoice number, a series format that sorts correctly and never collides, and how to handle gaps, restarts and multiple series.
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Questions people ask
No — that produces several invoices numbered 001 in the same financial year, and the requirement is that the number is unique for the year. Use one series across all clients and put the client in the name and body of the invoice, not in the number.
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