Invoice numbers and payment terms for contractors
Published
Two small details make an invoice easy to handle: a number nobody else has used, and payment terms that say exactly what is due and when. Get both right and you spend less time answering questions and chasing money.
Why the number matters
The invoice number is how you and your customer refer to a document. It lets you find an invoice years later and tells your accountant which documents belong to which period. Some countries also require invoice numbers to follow certain rules, so check what applies to your business.
Simple numbering schemes
- A plain running number: 0001, 0002, 0003
- A year and a running number: 2026-001, 2026-002
- A prefix for a business line or site, if you run more than one: RES-0001 and COM-0001
Pick one scheme and keep to it. Do not reuse a number, and do not edit an invoice you have already sent. If something was wrong, issue a corrected document and keep the old one on file, in line with the rules where you work.
Drafts are not invoices
Keep unfinished invoices apart from issued ones. A number should be given to a document when you send it, so that your sequence has no gaps caused by drafts you abandoned.
Write clear payment terms
- The total due and the currency
- A specific due date, not just "on receipt"
- How to pay: bank details, a reference to quote and any other methods you accept
- Any deposit already paid and the balance left
- The terms for stage payments if the job is billed in steps
If you charge for late payment, say so on the invoice and on the estimate, and only in a way that is allowed where you work.
Send promptly and follow up
Send the invoice as soon as the work or the stage is done. Follow up once the due date has passed, politely and in writing, and keep a note of what you sent.
Invoices in SiteReporta
In SiteReporta you mark an estimate as accepted and convert it to an invoice with identical totals, then add your bank details to the PDF. It does not take payments or track whether an invoice was paid, so keep your own record of what has been paid. Read estimate vs invoice for how the two documents differ.
General guidance, not legal, tax or accounting advice. Rules differ by country and trade.