How the number is built
An invoice number in this tool has up to three parts, joined by the separator you choose:
| Part | Example | What it is for |
|---|---|---|
| Prefix | INV | Makes invoices easy to recognize in email and file names |
| Date | 2026 | Shows the year (or year and month) an invoice belongs to |
| Sequence | 0042 | The running number that makes each invoice unique |
So a prefix of INV, the year, a hyphen and four digits gives INV-2026-0042. Leave the prefix empty and choose no date for a plain 0042.
The sequence is padded with zeros to the number of digits you choose, so that invoices sort in the right order in folders and spreadsheets: INV-0009 comes before INV-0010, where INV-9 would sort after INV-10.
Choosing a format
- Just starting? INV-0001 is enough. You can add the year later, at the start of a new year.
- Many invoices a year? INV-2026-0001 keeps each year’s invoices together and easy to find.
- A trade with its own convention? Use it: RO-10583 for repair orders, or your initials.
Whatever you choose, keep the two rules: every number unique, and each one following the last. How to number invoices explains why, and what to do with cancelled invoices.
What happens next
Use this number in your invoice opens the invoice generator with a new invoice carrying that number. From then on the generator suggests each next number for you: it finds the highest number among your saved invoices and adds one, keeping your prefix, date and zero padding. Your saved invoices are not changed.
If you include a year and want to restart the sequence each January, change the first invoice of the new year by hand (INV-2027-0001); the generator continues from there.