An invoice is a request for payment that also works as a record: for you, for your client’s accounts team, and for whoever does your tax. Getting it right is mostly a matter of including the same few things every time and sending it promptly.
Agree the terms before you start
Most late payments start before the work does. Before the first hour, agree in writing:
- your rate, or the fixed price and how it is split into payments;
- how long the client has to pay (14 or 30 days are common);
- who the invoice goes to, which is often an accounts address and not the person you work with;
- whether the client needs a purchase order number on the invoice.
A purchase order number left off an invoice is one of the most common reasons a large company sends it back unpaid.
What to put on the invoice
- The word “Invoice” and a number. Numbers run in order and are never reused.
- Your name, business name and address, and your tax registration number if you have one.
- The client’s name and address, as they want it written.
- The date you issue it, and the date it is due. “Due 14 November” is clearer than “30 days”.
- What you did. One line per task or per entry, with the date, the hours and the rate, or the fixed amount for that part of the work.
- The subtotal, any tax, and the total, with the currency.
- How to pay you: bank details, or a payment link.
The rules differ by country: some require particular wording, a tax number, or tax shown in a set way. Check what applies where you work. This guide is general advice, not tax advice.
Number invoices so they never collide
Give every invoice a number one higher than the last. A short prefix helps when you search your email later: INV-0142, or a year, 2026-0142. Never reuse a number, even for an invoice you cancelled. If an invoice was wrong, issue a corrected one under a new number and keep the old one on file.
Turn your hours into lines
If you bill by the hour, the invoice should let the client check the time. A line per task, with its date and hours, answers most questions before they are asked. “Homepage copy, 3 Oct, 2.5h at $60” is easier to approve than “Website work, 40h”.
For fixed-price work, bill in agreed parts: a deposit before you start, then on milestones or on delivery. Each invoice names the part it covers, and how much of the total is left.
Send it the day the work is done
The longer an invoice waits, the later it is paid, because the payment clock only starts when it arrives. Send a PDF, so the layout survives every email app, from the address the client knows. Put the invoice number and the amount in the subject line: “Invoice INV-0142, $2,320.50, due 14 November”.
Chase it politely, and on a schedule
A friendly reminder on the due date gets most late invoices paid. If a week passes, write again and ask whether anything is holding it up, which often turns up a missing purchase order or a wrong address. Keep each message short and attach the invoice every time, so nobody has to search for it.
Fixing a mistake
Do not edit an invoice the client already has. Issue a corrected invoice, or a credit note for the difference, so both sets of records match. Your accountant will thank you.
How Involets does it
In Involets you tick the unbilled hours on a project and each becomes a line at the project’s rate, with its date. Your tax, payment terms, invoice numbering and payment details are filled in, and you download a PDF with your logo. Once you have sent it from your own email you mark it sent; Involets then watches the due date and flags the invoice when it is overdue. A wrong invoice can be rolled back, which returns its hours to unbilled so you can make a corrected one. Involets does not email invoices or take payments: the invoice comes from you, and the money goes straight to you.
See Invoicing, or the help centre’s Create an invoice and Invoice numbers and due dates.