Free tool
Invoice number generator
Make a run of sequential invoice numbers in the format you choose, or type the last number you used and get the ones that follow. Works in your browser, no signup.
Generate invoice numbers
Next invoice number:
Runs in your browser; nothing you type is sent anywhere. The register CSV has a column for the number plus empty columns for the client, date, amount and status, so you can record each invoice as you send it.
How the generator builds a number
Each number is the parts you choose, joined by the separator, with the counter at the end padded with zeros to the number of digits you set. With the defaults that is INV-2026-0001, then INV-2026-0002 and so on. The year comes from your device’s date.
To continue a sequence, type the last number you actually used. The generator counts on from its last group of digits and keeps everything else as it was, including the zero padding: INV-2026-0147 is followed by INV-2026-0148, and 2026/099 by 2026/100. If a run would outgrow the padding (from 9999 to 10000), it warns you, because numbers of different lengths stop sorting in order.
Which format to choose
| Format | Example | Generator settings |
|---|---|---|
| Prefix + sequence | INV-0001 | Prefix INV, date part None |
| Year + sequence | INV-2026-0001 | Prefix INV, date part Year |
| Year and month | INV-202611-001 | Date part Year + month, 3 digits |
| Client prefix | ACME-0001 | Prefix empty, date part None, client code ACME |
| Short, for India GST | 26/0001 | Prefix empty, Short year, slash, 4 digits |
The pros and cons of each, and how to fix a gap or a duplicate, are in invoice number format: examples and rules.
Sequential, not random
Some generators offer random invoice numbers. Where tax rules mention invoice numbers, they ask for a sequence, so a random number can fail them:
- United Kingdom. A VAT invoice needs a unique number that follows on from the previous invoice’s number (HMRC: VAT Notice 700/21 (record keeping)).
- European Union. The VAT Directive asks for a sequential number, in one or more series, that identifies the invoice uniquely (Council Directive 2006/112/EC (VAT Directive), Article 226(2)).
- India. A GST tax invoice needs a consecutive serial number of no more than 16 characters, using letters, digits, “-” and “/”, unique for the financial year (CBIC: CGST Rules 2017, rule 46 (tax invoice)). The generator warns when a number breaks either limit.
- United States, Canada and Australia. The official guidance we checked does not list an invoice number as a required item; a sequence still makes your records easy to check. See invoice requirements by country.
Let the invoice keep count
If you make your invoices in Billpad, you only need the first number. Type it into the invoice generator; after each download, Next № moves to the following number in the same format. Receipts, estimates and proformas keep separate counts, so the receipt generator continues its own RCT- series. Billing many families or clients at once? Monthly invoices in bulk shows a numbering scheme for a batch.
Invoice number questions
What is an invoice number?
A unique reference printed on each invoice so that you, your client and anyone checking your books can identify it. Most businesses number invoices in order, such as INV-0001, INV-0002.
Can I start my invoice numbers at a number other than 1?
The rules quoted above ask for numbers that are unique and follow on; they do not set a starting number. Set Start at to any number, and keep counting on from there.
Can I restart numbering every year?
Yes, if the year is part of the number so that each one stays unique, as in INV-2026-0001 and INV-2027-0001. India’s rule says unique for the financial year (CBIC: CGST Rules 2017, rule 46 (tax invoice)).
Should quotes and receipts use the same numbers as invoices?
Give them their own series, such as EST- for estimates and RCT- for receipts, so an estimate never leaves a gap in your invoice numbers.
Is the invoice number generator free?
Yes, with no signup and no limit on runs other than 1,000 numbers at a time.
Updated 5 November 2026. General information, not legal or tax advice. Spotted an error or an outdated rule? Contact us. About Billpad.