Invoice Number Generator
Every invoice needs a unique number in an unbroken sequence. Paste the last number you used and get the next ones in exactly the same format, or design a new scheme from a prefix, the year or date, an optional client code and a zero-padded sequence. The tool lists up to 100 consecutive numbers ready to copy.
- Runs in your browser
- No sign-up
- Free to use
Next invoice number
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Numbers are created in your browser and are not stored. Keep your own record of the last number you issued: an invoice number must never be used twice.
How to use Invoice Number Generator
- To continue a series, enter the last invoice number you issued.
- To start a new series, choose prefix, separator, date part and sequence length.
- Choose how many numbers you want.
- Copy the next number into your invoice, or download the list.
Invoice Number Generator features
Continues any format
Counts up the last group of digits and keeps prefix, padding and anything after it.
Format builder
Prefix, separator, year or full date, client code and a sequence of two to six digits.
Batch output
One number or a list of up to 100 consecutive numbers.
Helpful warnings
Flags sequences that will outgrow their padding and series that carry last year’s date.
Nothing stored
Runs in your browser; your numbering stays with you.
Works with the invoice tool
Use the number in the Invoice Generator on this site.
When to use Invoice Number Generator
- Finding the next number when invoicing by hand or in a spreadsheet.
- Setting up a numbering scheme for a new business.
- Starting a new series at the beginning of a financial year.
- Creating separate series per client or project.
Invoice Number Generator FAQ
What are the rules for invoice numbers?
In most countries each invoice must carry a unique number from a sequence without gaps or repeats. The exact format is yours to choose. Requirements differ by country, so confirm with your tax authority or accountant, especially for VAT or GST invoices.
Can I restart the numbers every year?
Usually yes, provided the year is part of the number so that each number is still unique, for example INV-2026-001 followed next January by INV-2027-001.
Do the numbers have to start at 1?
No. Many businesses start at 100 or 1000. What matters is that numbers follow each other without gaps from wherever you start.
Why pad with zeros?
Zero-padded numbers have the same length and sort correctly as text: 009, 010, 011. Without padding, 10 sorts before 9 in file lists and spreadsheets.
What if I skip or cancel a number?
Do not reuse or delete it. Keep the cancelled invoice on file marked as void, or issue a credit note, so the sequence remains complete for an audit.
Does this tool remember my last number?
No. Nothing is saved. Your invoicing software or your own register is the record of the last number issued.
Why invoice numbers are sequential
An invoice number is more than a label. It is the reference customers quote when they pay, the key your bookkeeping uses to match payments to sales, and the evidence a tax auditor uses to check that no sales are missing. A sequence with no gaps and no repeats shows that every invoice issued is accounted for.
That is why most tax systems require invoices to be numbered consecutively and uniquely. Within that rule the format is free. The simplest is a plain running number. Adding a prefix distinguishes invoices from quotes, orders and credit notes. Adding the year lets you restart the sequence each January while keeping every number unique and making the age of an invoice obvious at a glance.
Some businesses add a client or project code, which helps when invoices are filed by customer. If you do, decide whether the sequence runs across all clients or separately for each; both are acceptable as long as no number can occur twice. Avoid encoding too much: long numbers are mistyped in bank transfers, and a scheme you cannot keep up consistently causes more trouble than it saves.
Whatever you choose, change it rarely and document it. Keep a register of the last number issued, never reuse a number, and keep cancelled invoices instead of deleting them. If you move from hand numbering to invoicing software, set the software to continue from your last number so the series carries on without a break.