Free Invoice Number Generator

What is an invoice number?

An invoice number is a unique reference on each invoice you send. It helps you, your client, and your accountant find a specific document in records, emails, and bank statements.

How this generator works

1. Choose a prefix: Add an optional prefix such as INV, a client code, or a year. The prefix appears before the number, separated by a hyphen.
2. Set the start number: Enter the first number in your sequence. Use the next unused number in your existing series to avoid duplicates.
3. Choose padding: Padding adds leading zeros so numbers stay the same length, for example 0001 instead of 1.
4. Choose how many to generate: Pick how many sequential numbers you need in one batch, up to 100.
5. Build each invoice number: Each result combines the prefix, a hyphen (when a prefix is set), and the padded number. Numbers increase by one for each entry in the batch.

Worked example

With prefix "INV", start number 1001, padding 4, and count 3, you get INV-1001, INV-1002, and INV-1003. With no prefix, start 42, padding 3, and count 2, you get 042 and 043.

When to use this generator

Use it when starting a new numbering system, reserving a block of numbers for upcoming invoices, or checking how a prefix and padding will look before you update your records.