What to include in an invoice

The 11-point checklist

The fields are not bureaucracy. An invoice is the formal request for payment for goods or services already supplied; it fixes the amount owed, the due date and the tax. The document only carries that weight if the parties, the items, the amounts and the dates are unambiguous.

1. Invoice number. Sequential and unique; required by tax law in most countries and the anchor for payments, credit notes and receipts. Example: INV-2026-0918
2. Issue date. Starts the clock for validity, delivery and payment terms; for invoices it usually sets the tax point. Example: 18 September 2026
3. Due date. A date is harder to ignore than 'net 30' and removes any argument about when the payment was late. Example: Due 18 October 2026
4. Seller name, address and contact. Identifies who is supplying and who to contact about the document. Example: Northgate Joinery Ltd, 14 Mill Lane, Leeds LS1 4AB, accounts@northgatejoinery.co.uk
5. Buyer name, address and contact. Identifies who is ordering or paying; on invoices the legal entity name matters for tax. Example: Harbour Café Ltd, 3 Quay Street, Bristol BS1 6XN
6. Buyer's PO reference. Without it the buyer's accounts payable cannot match the document to an authorised order and will park it. Example: Your PO: PO-2026-0142
7. Line items. Description, quantity, unit price and line total for each item, so both sides can check the arithmetic. Example: 12 × oak worktop 3 m @ $185.00 = $2,220.00
8. Subtotal, tax and total. Shows the tax separately so the buyer can reclaim it and the seller can report it. Example: Subtotal $2,220.00, VAT 20% $444.00, total $2,664.00
9. Payment terms. States when and how payment is expected; on quotes and POs it sets expectations, on invoices it is enforceable. Example: 50% deposit on order, balance within 14 days of delivery
10. Bank details. Removes the email round-trip that delays most first payments; verify them by phone if they ever change. Example: Account name Northgate Joinery Ltd, sort code 40-12-34, account 12345678
11. Tax registration numbers. Required on tax invoices in most countries for the tax to be reclaimable. Example: VAT no. GB 123 4567 89

Numbering

On numbering: Sequential and unique by law in most countries; gaps and duplicates are the first thing an auditor looks for. Never reuse a number, and never renumber after the document has been sent.

What it does in the accounts

What the invoice does to the books: it is revenue for the seller, a liability (accounts payable) for the buyer, and the tax point for VAT or sales tax. Get the date and the totals right on the document itself; correcting them later means issuing another document, not editing this one.

The mistake to avoid

Watch for one error above all: reissuing a corrected invoice under the same number instead of cancelling it with a credit note. It is usually a template problem, so fix the template rather than the individual document.

Make an invoice now with the Invoice Maker; it carries every one of the 11 fields on this list and runs in your browser.

Compare it with the documents it is most often confused with: Quote vs invoice, Quote vs proforma invoice, Proforma invoice vs invoice, Purchase order vs proforma invoice.