An invoice has one job: give the person paying you everything they need to approve the payment without asking you a question. Every follow-up email — "which project is this?", "what's your account number?", "can you add our PO number?" — is a week of delay caused by a missing line. Treat the document as a form for someone else's accounting system, not as a letter.
The header: who is billing whom
Two blocks, side by side. The Bill From block is your legal or trading name, your address, an email that you actually monitor, and a phone number. If you operate as a registered company or have a tax registration number, it belongs here — accounts departments frequently cannot process an invoice without it.
The Bill To block is the part people get wrong. Address the invoice to the entity that owes the money, not the person who briefed you. A creative director asked for the work; the holding company pays for it. If the billing entity has a slightly different legal name from the brand you dealt with, use the legal name and ask for it in writing before the first invoice. Where you know it, include an attention line ("Attn: Accounts Payable") or the internal contact who approves spend.
Invoice number
A unique identifier, never reused. It is how both sides refer to the payment in every subsequent email, bank reference and remittance advice. Numbers should never collide and, in most bookkeeping regimes, should not have unexplained gaps. This deserves a real system rather than a guess each month — see the invoice numbering guide.
Dates: issue date and due date
The issue date is when you raised the invoice; it usually determines which tax period the income falls into. The due date is the date payment is expected. Write both as explicit calendar dates, not as "Net 30". Payment terms are a policy; a due date is a deadline, and only one of those shows up in a payment run.
Ambiguous date formats cause real delays when you and the client are in different countries. 10/03 means March in one place and October in another. Spell the month out where you can, or use the ISO form (2026-03-10).
Description of what you did
Write the description for someone who was not in the room. "Design work" is not approvable. "Brand identity refresh — logo lockups, colour system and 24-page guidelines, delivered 14 July" is. Where the work was quoted or contracted, echo the exact wording from the quote so the approver can match it against the document they signed.
Useful things to include in the description when they apply:
- The purchase order or job number the client gave you.
- The period covered, for retainers and ongoing work.
- The deliverable and the date it was handed over.
- Anything out of scope that was agreed by email, with the date of that agreement.
The amount
State the figure once, clearly, with the currency written explicitly. "$1,200" is not enough information if you work with clients in the United States, Canada, Australia and Singapore — write "USD 1,200.00". Include the currency code even when you think it is obvious, because the person keying it into the banking portal has no context.
Writing the amount in words alongside the digits is an old banking convention that still earns its keep: it removes any doubt about a misplaced decimal point or a smudged digit in a printed copy, and it makes tampering obvious. InvoiceGen generates the words automatically from the figure you type, so the two can never disagree.
Payment method and bank details
The single most common cause of a late payment is an invoice that does not say how to pay it. Include everything the payer's system needs: account name, account number, sort code / routing number / IFSC, IBAN and SWIFT for cross-border transfers, or your UPI ID where that applies. If you accept more than one method, list them in the order you prefer, and say which reference the payer should use — normally the invoice number.
Notes and terms
A short notes block is where you put the things that are true but not part of the arithmetic: thanks for the work, what happens if payment is late, and any conditions attached to the delivery. Keep it to two or three lines. A wall of terms at the bottom of an invoice is skipped by everyone, including the person you wrote it for; substantive terms belong in the contract you signed before starting.
Before you send it
- Read the client's legal name back against their contract or website footer.
- Check the total against your quote, including any agreed extras.
- Confirm the due date is a working day and matches your agreed terms.
- Confirm the bank details are yours and current — copy them from your bank, not an old file.
- Send to the accounts address, and copy your day-to-day contact so someone chases internally.
- Attach a PDF. Never send an editable document as the invoice of record.
Why PDF matters
A PDF renders identically everywhere and cannot be accidentally edited by the recipient. A word processor file reflows the moment a client name grows by one character, and a spreadsheet may show different figures depending on locale settings. Generate the PDF, keep a copy, and treat that file as the record of what you sent. The generator produces exactly what the preview shows, and stores a copy in your browser so you can re-download it later.