How to Write an Invoice: What to Include (and What Gets You Paid)
· by Andergrove Software
An invoice has one job: to get you paid without a follow-up conversation. Most late payments aren't malice — they're an invoice sitting in someone's inbox missing the one detail (a due date, a bank account, a PO number) that would have let them approve it on first reading. Here is what a complete invoice contains, and the handful of conventions that make the difference between "paid this week" and "chasing it next month".
What must an invoice include?
Every invoice needs nine things: the word "Invoice", a unique invoice number, the issue date, a due date, your business name and contact details, the client's name and address, itemised charges with quantities and prices, any tax shown as its own line, and payment instructions. Miss any of them and you have given someone a reason to put it aside.
Two of the nine do the most work. The unique number is what lets both sides refer to the invoice unambiguously — in emails, in remittance advice, in bookkeeping. And payment instructions are the step people underrate: the person approving your invoice is often not the person paying it, so the paying person needs the account details, the reference to use, and the amount, all on the document itself.
Invoice numbers: pick a scheme that scales
Any scheme works as long as numbers are unique and roughly sequential. Three that hold up:
| Scheme | Example | Good for |
|---|---|---|
| Plain sequence | INV-042 | Sole traders, low volume |
| Year + sequence | INV-2026-042 | Most freelancers and small businesses — resets yearly, sorts perfectly |
| Client + sequence | ACME-011 | A few big clients with their own AP systems |
Start at something other than 001 if you would rather not advertise that a client is your first. Never reuse a number, even for a cancelled invoice — issue a credit note or skip it.
Payment terms: what Net 30 actually means
"Net 30" means the full amount is due 30 days after the invoice date — not after the client gets around to reading it. The common terms:
| Term | Meaning |
|---|---|
| Due on receipt | Payable immediately — normal for small jobs and first engagements |
| Net 7 / 14 / 30 | Due that many days after the invoice date |
| 2/10 Net 30 | 2% discount if paid within 10 days, otherwise full amount in 30 |
| EOM / 20 MFI | End of month, or the 20th of the month following — common in trades |
Whatever you choose, also print the actual due date. "Net 30" makes the client compute a date; "Due 21 August 2026" removes the excuse. If you charge late fees, say so on the invoice ("Overdue balances accrue 1.5%/month") — you may never collect a cent of it, but it visibly changes queue position in accounts payable.
Tax lines: GST, VAT and sales tax
If you are registered for a consumption tax — GST in Australia and New Zealand, VAT in the UK and EU, sales tax in US states — show the subtotal, the tax as its own labelled line with the rate, and the total. Business clients need the split to claim the tax back, and several jurisdictions legally require it, along with your registration number (ABN, VAT number, and so on) on the invoice itself. If you are not registered, don't invent a tax line; just invoice the amount. The rules for whether to charge are jurisdiction-specific — that part is your accountant's job, not your template's.
The small things that speed up payment
- Include the client's PO number if they issued one — large companies' AP systems can't match an invoice without it, and "missing PO" is the most common silent rejection.
- Address a person, or at least the right inbox (accounts@, not your project contact who forwards it eventually).
- Attach a PDF, not a link — links to portals and editable documents get flagged, filed and forgotten; a PDF gets processed. Name the file after the invoice number.
- Invoice promptly. The correlation between invoicing fast and being paid fast is boringly strong; the clock starts when you send it, not when you finish the work.
- Itemise honestly. Three specific lines beat "Services rendered — $4,000" — vague invoices invite queries, and queries reset the clock.
A template you can use right now
Our free invoice generator produces exactly the document described here: numbered, dated, itemised, tax shown separately, notes for your bank details — downloaded as a clean PDF named after the invoice number. It runs entirely in your browser, so your client list and rates stay on your machine (the form auto-saves locally for the next one), and there is no signup, watermark or upsell attached. Fill it in, download, send, get paid.