Free tool

Invoice number generator

Pick a format that scales. Sequential, year-based, year-month-based, or custom. Get the next ten numbers, ready to paste into your books.

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An invoice number is a unique identifier for every invoice you send. It must be sequential, never repeat, and ideally include enough metadata (year, prefix) that you can find any invoice by name a year later. The IRS, HMRC, and most tax authorities require sequential numbering on issued invoices. This generator builds the next batch in any of the four common formats so you can paste them into your spreadsheet or accounting tool.

Next 10 invoice numbers

Why a numbering scheme matters

Your numbering scheme is invisible until tax time, then it is the most important field on the invoice.

Tax authorities require sequential numbers

The IRS, HMRC, and most VAT regimes require that invoices be numbered in an unbroken sequence per legal entity. Skipping a number forces you to keep a record of why.

Year-based formats make audit prep painless

INV-2026-001 sorts naturally and tells you the issue year at a glance. A pure sequential like INV-12847 hides that information.

Padded numbers sort correctly

INV-9 and INV-10 sort wrong in most spreadsheets because the system reads them as text. INV-009 and INV-010 sort correctly. Padding to 3 or 4 digits future-proofs you.

Mid-year format changes are messy

Switching from sequential to year-based mid-year creates a numbering gap. Decide once at the start of a fiscal year, then keep it stable.

What to do with these numbers

Generate the invoice itself

Drop the number into our free invoice generator and send a real, shareable invoice in under a minute.

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Validate the buyer's PO format

Before you send, check that the PO your client gave you matches a recognized AP format.

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Use custom numbering in the product

JupiterInvoice's paid tier lets you set the format once and increments it for every new invoice automatically.

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Invoice number generator FAQ

Are invoice numbers legally required?

Yes in most jurisdictions. The IRS, HMRC, the EU VAT directive, and Canada's CRA all require that invoices issued by a registered business carry a unique, sequential identifier.

Can I skip a number?

Generally no. If you void an invoice, keep the number on file with a 'voided' note. Skipping numbers without a voided record will be flagged in an audit.

What format should I pick?

Year-based (INV-2026-001) is the most common and the easiest to audit. Sequential (INV-0001) is fine if you do low volume. Year-month or date-based formats are useful if you issue many invoices per day.

Should I include the customer name in the number?

We recommend not. Customer names change, and embedding them in the invoice number creates a parallel naming system that drifts over time. Use the prefix for your business identifier and store the customer separately.

How many digits of padding do I need?

Three digits (001) covers up to 999 invoices per year. Four digits (0001) covers up to 9,999. Pick the next size up from your current annual volume.

Can JupiterInvoice keep my numbers in sequence automatically?

Yes. The paid tier includes custom invoice numbering: set the format and starting number once, and every new invoice increments automatically. The free tier uses a default scheme you can override per invoice.