Invoice number
A unique identifier for this invoice. Most jurisdictions require it to be sequential within a controlled series (e.g. INV-0001, INV-0002, …). You can use prefixes for client groups or years, but never reuse a number and never reset the sequence mid-year unless your local tax rules explicitly allow it.
The invoice number is what both parties use to track the document — in your books, in the buyer's accounts payable system, and on payment references. Make it short, legible, and consistent.
Issue date and due date
The issue date is the day you raise the invoice. The due date is the day payment is expected. Both should appear explicitly, as calendar dates, near the invoice number.
Resist the urge to write only 'Net 30' as the term. Convert it to a date ('Due 15 April 2025') so there is no ambiguity about whether 'days' means calendar or business days.
Customer and seller details
The customer's legal name, billing address, and contact email belong in their own block, opposite your own seller details. A first name and a personal email is not enough for a B2B invoice — accounts payable need the legal billing entity to process it.
If the buyer trades under a different name from the legal entity, use the legal entity on the invoice and reference the trading name only if needed for clarity.
Line items: description, quantity, unit price, line total
Each line should describe a deliverable specifically enough to match the contract or purchase order. Quantity and unit price let the buyer verify the math; line total is the per-line subtotal before tax.
Keep line items granular enough to be matchable but not so granular they overwhelm the reader. One line per deliverable is the right unit, not one line per email.
Subtotal, tax, and total
The subtotal is the sum of line totals before tax — this is the 'net amount'. The tax line should show the rate and the calculated amount. The final total ('gross amount') is the figure the buyer is asked to pay.
Even when tax is zero, show the line and explain why ('Reverse charge — VAT to be accounted for by the recipient', 'Out of scope of UK VAT', etc.). A blank tax line raises more questions than a labelled one.
Payment instructions
Bank transfer details (account name, IBAN or sort code and account number, payment reference), card or wallet payment link, and any other accepted methods. The reference field matters: tell the buyer to use the invoice number so reconciliation is automatic on your end.
Place this block on page one, near the totals. Footers are read by very few accounts payable teams.
Notes and terms
Use the notes field for genuinely useful context: a thank-you line, a project reference for the buyer's records, or a short note on what the next invoice will cover.
Terms should be referenced succinctly — 'Statutory late interest applies after the due date' is enough for most cases. Long terms blocks belong in a separate document the invoice references.
Worked example
Invoice INV-0042 issued 1 March, due 15 March. Customer: Acme Ltd, 12 High Street, London. Line: 'Brand identity design — Phase 1 of 2 (1 of 2 milestones), 1 × £2,400.00, line total £2,400.00'. Subtotal £2,400, VAT 20% £480, total £2,880 GBP.
Payment block: 'Bank transfer to Studio Doe Ltd, sort code 12-34-56, account 12345678, reference INV-0042. Card payment: [link].' Notes: 'Phase 2 of 2 will be invoiced on completion in late April. Thank you.'
Every field above is doing a job. Remove any one and the invoice gets harder to act on.