Invoice number generator — sequential numbers by year or financial year

How to use the invoice number generator

1. Type a Prefix, such as INV, or your initials. Leave it blank for numbers only.
2. Choose the Year part: Year (2026), Short year (26), Financial year April–March (2026-27), Short financial year (26-27), Year and month (202610) or None.
3. Set the Invoice date, which decides the year part.
4. Enter the First number, the width to Zero-pad to, and a Separator (up to three characters).
5. Set How many numbers (up to 5,000) and press Generate. Copy the list.

What it does and when to use it

Freelancers, small firms and accounts teams need a numbering scheme that is easy to read, sorts correctly and never repeats. Putting the year in the number makes it clear which period an invoice belongs to, and zero-padding keeps INV-0009 before INV-0010 in any sorted list. This tool shows the scheme before you commit to it, and gives you a block of numbers for a paper invoice book, a spreadsheet or an import into accounting software.

Every list ends with the reminder that “Most tax authorities expect invoice numbers to be unique and sequential within a series — continue from your last issued number.” For order references, which can be random, use the order number generator. For other labels, the serial number generator works from a pattern. To check a customer’s bank details on an invoice, the IBAN generator has a validator.

How it works

Each number is the prefix, the year part and the counter, joined by the separator, with empty parts left out. The counter starts at First number, goes up by one for each line, and is padded with leading zeros to the chosen width. It is never cut short, so 10000 with a width of 4 stays 10000.

The year part comes from the invoice date. For the financial-year formats, a date in April or later starts a new year; January to March belong to the year that began the April before.

Worked examples

• Calendar year. Invoice date 2 October 2026, defaults: INV-2026-0001, INV-2026-0002, INV-2026-0003.
• Financial year with slashes. Date 10 February 2027, separator /, first number 42: INV/2026-27/0042.
• Year-end edge. Short financial year on 31 March 2026, first number 118: INV-25-26-0118 and INV-25-26-0119.
• Numbers only. Year and month, no prefix, no separator, width 3, on 7 October 2026: 202610001 and 202610002.

Limits and tips

• Some tax systems limit the length or the characters of an invoice number. Check before you choose a long prefix or unusual separators.
• Avoid reusing a number, even for a cancelled invoice; the usual fix is a credit note.
• Keep one series per business or branch, and record the last number you issued.