Free invoicing tool
Invoice Number Generator
Generate clean, sequential invoice numbers with custom prefixes, year and month tokens, and zero-padding. Free, instant, and no signup — then create the full invoice in one click.
Build your invoice number
Your next invoice number
Upcoming series
- →INV-2026-0001
- ·INV-2026-0002
- ·INV-2026-0003
- ·INV-2026-0004
First invoice PDF is free — no signup required.
How to generate an invoice number
Pick your format
Choose a prefix (INV), and whether to include the year or month. Set how many digits the sequence uses.
Set the starting number
Start at 1, or at a higher number like 1000. The tool zero-pads and previews the next numbers in the series.
Copy and create the invoice
Copy the number, or continue to the free invoice generator — Invoicey auto-increments it on every new invoice.
Invoice number formats and examples
There is no single legally required format — the rule that matters is that numbers are unique and sequential. These are the formats freelancers and small businesses use most. Pick one and keep it consistent across every invoice.
Why sequential invoice numbering matters
Tax authorities in the UK, France, Germany, and across the EU require invoice numbers to form a continuous series with no gaps and no duplicates. During an audit, missing or repeated numbers are a red flag — they suggest invoices were deleted or issued off the books. A clean sequence is the simplest way to show your records are complete.
Sequential numbering also keeps your own bookkeeping sane: invoices sort in the order you issued them, payment chasing is easier, and reconciling against your bank statement is faster. Adding a year prefix (2026-0001) lets you reset the count each tax year while keeping every series unique.
The safest approach is to never assign numbers by hand. When you create invoices with Invoicey, the next number in your chosen format is filled in automatically, so you can’t accidentally skip or reuse one.
Frequently Asked Questions
What is an invoice number?
An invoice number is a unique identifier assigned to each invoice you issue. It lets you, your client, and your accountant reference a specific invoice for payment, bookkeeping, and tax records. Most tax authorities require invoice numbers to be unique and sequential (no gaps and no duplicates).
Do invoice numbers have to be sequential?
In most countries — including the UK, France, Germany, and across the EU — invoice numbers must follow a sequential series with no gaps. You can reset the sequence per year (e.g. 2026-0001) as long as the numbering within each series is continuous and every number is unique.
What is a good invoice number format?
A clear format combines an optional prefix, an optional year or month, and a zero-padded sequence — for example INV-2026-0001. The prefix identifies the document type, the year groups invoices for accounting, and the padded sequence keeps them sortable. Pick one format and keep it consistent.
Can I start my invoice numbers at any number?
Yes. Many businesses start at 1 (INV-0001), but you can start at any number — for example 1000 — so early invoices look more established. The only rule is that once you choose a starting point, the series must continue sequentially without duplicates.
Should I reset invoice numbers each year?
You can, and many freelancers do — a year prefix (2026-0001, 2026-0002…) makes it easy to find invoices for a given tax year. This is allowed as long as each yearly series is itself continuous and unique. Just be consistent: don’t mix reset and non-reset schemes in the same year.
Is this invoice number generator free?
Yes. The invoice number generator runs entirely in your browser, with no signup and no limits. When you’re ready to issue the actual invoice, you can create and download a professional PDF with Invoicey’s free invoice generator.
How do I avoid duplicate invoice numbers?
Use a single, consistent format and always increment from the last number you issued. A padded sequence (0001, 0002, 0003) prevents accidental reuse and keeps invoices sorting correctly. Invoicey auto-increments the number for you on every new invoice so duplicates can’t happen.