What actually has to go on an invoice

An invoice is valid because of what it says, not what produced it. Whether it comes from enterprise accounting software or a free generator, these are the parts that matter:

• The word "Invoice." Sounds obvious, but it's what distinguishes a bill from a quote in a dispute.
• A unique invoice number. One per invoice, never reused. It's how you and your client refer to it later.
• Your details. Business name, address, and a tax registration number if you have one.
• Your client's details. The legal entity being billed — not just a contact's first name.
• Issue date, and the due date. "Due on receipt" is a due date; "soon" is not.
• A clear description of each item, with quantity and unit price. "Consulting" is weak; "Consulting — 4 hrs, site survey, 12 Jun" is strong.
• Subtotal, tax, and total. Show the tax rate separately, even when it's zero.
• How to pay. Bank details, payment link, or terms. A surprising number of late invoices are just invoices nobody knew how to pay.

Invoice, quote, estimate or pro forma?

Using the wrong one is the single most common way small businesses end up arguing about money.

• Estimate — your best guess before the work is scoped. Not binding, and should say so. Use it to start a conversation.
• Quote — a fixed price you're committing to, usually with an expiry date. Once accepted, it's effectively the deal.
• Pro forma invoice — looks like an invoice but isn't a demand for payment yet. Used for deposits, customs paperwork, and clients who need a document to raise a purchase order.
• Invoice — the actual request for payment. This is the one that goes in your books and starts the clock.
• Credit note — cancels or reduces an invoice you already issued. Issue one of these instead of deleting an invoice; your numbering should have no gaps.
• Receipt — confirms money was received. Not the same as an invoice, and some clients need both.

The editor has all six, each with the right wording and its own numbering sequence.

Payment terms that actually get you paid

Terms are a lever most people never pull. A few things that measurably help:

1. Shorten the window. Net 30 is a habit, not a law. Net 14 or "due on receipt" is normal for small suppliers and rarely questioned.
2. Give a date, not a duration. "Due 3 August 2026" beats "Net 14" — nobody has to do arithmetic, and nobody can pretend to have got it wrong.
3. Invoice immediately. The correlation between how fast you invoice and how fast you're paid is brutal. Same day beats end of month.
4. State the late fee, even if you never charge it. Something like "1.5% per month on overdue balances" changes how the invoice is triaged in an accounts payable queue.
5. Ask for a deposit on new clients. 30–50% up front on the first job filters out the accounts that were never going to pay.
6. Make paying trivial. Bank details on the invoice itself, not in a separate email.

How to chase a late payment without wrecking the relationship

Assume it's an oversight until proven otherwise — it usually is. A simple escalation:

• Day 1 overdue: a short, friendly note. Reattach the PDF. Most invoices get paid at this step, because the original genuinely got buried.
• Day 7: reply in the same thread, ask a direct question: "Can you confirm this is scheduled for payment, and for what date?" A question is harder to ignore than a reminder.
• Day 14: pick up the phone, and ask for accounts payable rather than your usual contact. Your contact often has no visibility of the payment run.
• Day 30: a formal notice — the amount, the original due date, the late fee if you have one, and a deadline before further steps.
• Beyond that: pause further work, then consider a formal demand or small claims. Both are cheaper than they sound and rarely needed once you've shown you keep records.

Keep every step in writing and in one email thread. If it ever escalates, that thread is your case.

Numbering and keeping records straight

Boring, and the thing your accountant will thank you for.

• Sequential, no gaps. 1, 2, 3 — or 2026-001. If you void one, issue a credit note rather than skipping the number.
• Never reuse a number. Even for a corrected invoice: the corrected one gets a new number that references the old.
• Separate sequences per document type. Quotes and invoices shouldn't share a counter.
• Keep the PDF you actually sent. Not the data it was made from — the file. That's the version your client has.
• Know your retention period. Many jurisdictions require you to keep records for six or seven years.

This is general information, not accounting or legal advice — rules differ by country and by business structure. For anything material, ask an accountant in your jurisdiction.