What to include on an invoice

The eight things every invoice needs

1. The word “Invoice” — visible at the top. Accounts-payable departments sort by document type; make yours unambiguous.
2. A unique invoice number. Required almost everywhere for tax purposes, and the reference every payment and dispute will use.
3. Your details — legal name, address, and any tax or VAT identifier your jurisdiction requires. If you operate under a business name, use it consistently.
4. Your client’s details — the legal entity being billed, not just your contact’s first name. Invoices addressed to the wrong entity bounce back weeks later.
5. Two dates: the issue date and the due date. “Net 14” means nothing until it is a calendar date on the page.
6. Line items — what you did, quantity or hours, unit rate, line total. Specific enough that a stranger in accounting can approve it without asking your contact.
7. Tax, shown separately — subtotal, tax rate and amount (or the applicable exemption note), then the grand total in an unmissable size.
8. How to pay you — bank details or payment link, plus the invoice number as the requested payment reference.

Numbering that scales past invoice #3

Any scheme works while you have one client. The one that still works at fifty is date-prefixed and sequential: 2026-014 — year, then a running count. It sorts chronologically in every file browser, never collides, and leaks nothing. (Starting at 001 tells your first client they are your first client; starting mid-sequence is a common and harmless convention.)

Never reuse or skip-and-reuse a number, even for a cancelled job. Tax auditors read gaps and duplicates as red flags; issue a credit note instead and keep the sequence intact.

The mistakes that delay payment

• No due date. An invoice without one enters the client’s “whenever” pile. State the date and, if you charge late fees, the terms.
• Vague line items. “Consulting — $2,400” invites a clarification email; the clarification email costs you a week.
• Wrong entity or missing PO number. If the client gave you a purchase-order number, it goes on the invoice; without it, larger companies’ systems simply cannot pay you.
• Editable formats. Send a PDF, not a spreadsheet or document file — both for professionalism and because nobody should be able to edit the total.

Do you need invoicing software for this?

For recurring billing, client portals and automatic reminders — eventually, maybe. For producing a correct, professional PDF: no. Be wary of the “free invoice generator” that watermarks the download, holds your invoice history behind a signup, or quietly turns into a subscription — the invoice is yours, and your client’s details should not live on a stranger’s server as the price of a PDF. A generator that runs locally in your browser covers the checklist above with nothing held hostage.