Invoice number generator
Preview and export a deterministic invoice identifier sequence with date and padding controls.
How it works & useful details
Formula & assumptions
Identifiers combine an ASCII letter/digit prefix, an optional explicit date segment and an integer sequence. Padding sets the minimum digit count and never truncates larger numbers. Date is a real calendar date from 1900–9999; batch size is 1–500; sequence values are 1–999,999,999. Each run starts from your entered number. This is not a uniqueness check, compliant invoice issuance or a stored counter.
Local planning workspace
These tools are planning aids, not financial, tax or legal advice. Values stay in this page. Nothing is sent, saved to your records or fetched from external services.
USD, EUR, GBP, CAD and AUD are labels with two decimal places. There is no currency conversion. Enter decimals with a dot and no commas. Money inputs are limited to 1 billion units; calculated amounts to 10 trillion. Rates are supplied by you, with up to four decimal places.
About this tool
Invoice number generator previews a consistent sequence of invoice identifiers using a prefix, an optional date component, and zero padding. Seeing the next numbers in advance makes it easier to keep your records sequential and avoid gaps or duplicates.
The sequence is deterministic: the same settings always produce the same output, and nothing is stored or registered. Copy the numbers into your invoicing tool or export the preview as text.
How to use it
- Choose a prefix and the starting number of the sequence.
- Set the number of padded digits and whether to include a date part.
- Review the previewed identifiers in order.
- Copy individual numbers or export the whole preview as text.
Worked example
With the prefix INV, the date 2026-09-24 in year-and-month form, a hyphen separator, a start number of 98, and three-digit padding, a batch of four produces:
INV-202609-098
INV-202609-099
INV-202609-100
INV-202609-101The next unreserved identifier is INV-202609-102. Padding sets a minimum width, so the sequence continues to 1000 and beyond instead of wrapping or truncating.
Choosing a numbering scheme
Many tax authorities require invoice numbers that are unique and follow a continuous sequence, without gaps you cannot explain. A date segment makes numbers easy to sort and file. A year-only segment is a common compromise. It resets naturally each year while keeping numbers short.
- Keep one sequence per legal entity, and do not reuse numbers after cancelling an invoice. Issue a credit note instead.
- Pick padding that fits your expected volume, such as four digits for up to 9,999 invoices per period.
- Record the last number you issued somewhere durable. This tool does not store a counter; each run starts from the number you enter.
Frequently asked questions
Does this reserve or track invoice numbers?
No. It only previews the identifiers from your settings; you remain responsible for issuing and recording them.
What do the padding settings do?
Padding adds leading zeros so numbers sort consistently, for example 0007 instead of 7.
Is anything saved on a server?
No. The preview is generated in the page and disappears when you refresh or reset.
Can I use a slash as the separator?
Yes, hyphen, underscore, and slash are available. Slashes look familiar on paper but cannot appear in file names, so a hyphen is safer if invoice numbers become PDF names.