What to include on an invoice

An invoice does two jobs: it tells a human what they owe and why, and it gives an accounts system enough information to process the payment without asking you a question. Most late payments that aren't about cash flow are about the second job being done badly.

The essentials

• The word "Invoice". Obvious, and regularly missing from documents that are really quotes with the heading changed.
• A unique invoice number. One per invoice, never reused, never out of order.
• Your business details. Name, address, contact, and any registration or tax number your country expects.
• The client's details. The legal entity being billed, not just the person you email. Large companies pay entities, not contacts.
• The issue date. The date the payment clock starts from.
• A description of the work. Specific enough that someone who wasn't in the room can approve it.
• Quantities, rates and line totals. Hours, units, or a single fixed-price line — but shown, not implied.
• Subtotal, tax and total due. Tax as its own line if you charge it.

The four that decide whether you get paid on time

• The due date, as a date. Not "Net 30" alone — a specific day. People pay dates; they negotiate terms.
• Payment details. Account number, sort code or routing number, IBAN, or a payment link. Whatever it takes for the money to move without a reply-all thread.
• A reference to quote. Tell them what to put on the payment so you can reconcile it.
• Their PO number, if they use one. In many companies an invoice without it cannot be processed at all.

Worth adding

A one-line thank-you, the period the work covers, and your late payment terms if you intend to enforce them. Keep it to a line each — an invoice is a document people scan, not read.

What to leave off

Long terms and conditions (link or attach them), apologies about the price, and anything that turns the document into a negotiation. The invoice is the end of the conversation about cost, not a new one.

Country-specific requirements

Tax-registered businesses usually have extra obligations: registration numbers, specific wording, particular details for higher-value sales. Those are set by your own tax authority, and this guide isn't tax advice — check what applies where you are before your first tax-registered invoice goes out.