Freelance Invoice Checklist: What to Include, Payment Terms and Follow-Up Emails

An invoice that's missing information gets paid late, or not at all. Here's a practical checklist, what UK rules require as a worked example, how to set payment terms, and polite follow-up wording you can copy.

The invoice checklist

Requirements differ by country, so treat this as a practical baseline and check your local rules:

• ☐ The word "Invoice" and a unique invoice number
• ☐ Issue date and the date the work was delivered (or the period it covers)
• ☐ Your name (and business name, if you use one), address and contact email
• ☐ Client's name and address, plus their PO or reference number if they gave you one
• ☐ A clear description of each item: what, how many, at what rate
• ☐ Subtotal, any tax (only if you're registered to charge it) and the total due, with the currency stated
• ☐ Due date written as a date ("Due 14 November 2026") as well as the terms ("14 days")
• ☐ How to pay: bank details or payment link, and the reference to quote
• ☐ Any deposit already received and the balance due

Most late payments are slow approvals, not refusals. An invoice that matches the client's PO, names the right contact and states the due date is easier for their accounts team to approve.

Example: what UK rules require

GOV.UK's guidance says an invoice must include a unique identification number, your company name, address and contact information, the customer's company name and address, a clear description of what you're charging for, the supply date, the invoice date, the amounts charged, VAT if applicable, and the total owed. Sole traders must also include their name and any business name, plus an address where legal documents can be delivered if they use a business name. If both you and your customer are VAT registered, you must issue a VAT invoice, which needs more information.^[1]

Other countries have their own lists. Search your national tax authority's website for "invoice requirements" before you send your first invoice.

Payment terms and late payment

State your terms on the quote and on the invoice. Common choices are 7, 14 or 30 days, or "due on receipt" for small jobs.

In the UK, for business-to-business sales, a payment is late 30 days after the customer receives the invoice (or after delivery, if that's later) unless you agreed a payment date. Agreed payment dates must usually be within 60 days for business transactions.^[2] If a business pays late, you can charge "statutory interest" of 8% plus the Bank of England base rate, unless your contract sets a different rate.^[3] Other countries have different rules. If you plan to charge late fees, put them in your terms before you start the work.

Practical ways to get paid on time:

• Take a deposit before starting larger projects.
• Invoice the day you deliver, not at the end of the month.
• Make paying easy: one clear method, the exact amount and the reference.
• Keep a simple invoice log with the due date and status, so nothing slips.

Invoice numbering that stays tidy

Pick a scheme and never reuse a number. A few options:

• Sequential: 0001, 0002, 0003…
• Year + sequence: 2026-001, 2026-002… (easy to sort by tax year)
• Client prefix: ACME-2026-01 (handy with many clients, but keep one overall sequence too)

If you make a mistake, don't edit an invoice you've already sent. Issue a credit note (or cancel it, following your local rules) and send a new one with a new number.

Follow-up emails you can copy

Keep reminders short and factual, and attach the invoice every time.

Friendly reminder (due date + 1–3 days)

Subject: Invoice [#] — due [date]

Hi [Name],

Just a quick note that invoice [#] for [project] ([amount]) was due on [date].
I've attached it again in case it got buried. Could you let me know when it's scheduled for payment?

Thanks,
[Your name]

Second reminder (about a week later)

Subject: Following up: invoice [#] ([amount]) now [N] days overdue

Hi [Name],

I'm following up on invoice [#] for [project], which is now [N] days past the due date of [date].
Is there anything you need from me (a PO number, a different format, another contact) to get it approved?

Payment details are on the attached invoice.

Thanks,
[Your name]

Firm reminder (overdue 2+ weeks)

Subject: Action needed: overdue invoice [#]

Hi [Name],

Invoice [#] ([amount]) is now [N] days overdue. Please arrange payment by [date, ~5 working days out].
As set out in my terms, [late fee / interest, only if your terms include one] applies to overdue invoices,
and I'll need to pause further work until the account is up to date.

If there's a problem with the invoice, reply and I'll sort it out straight away.

Regards,
[Your name]

1. GOV.UK, "Invoicing and taking payment from customers: Invoices – what they must include". gov.uk (accessed 16 Oct 2026).
2. GOV.UK, "Late commercial payments: When a payment becomes late". gov.uk (accessed 16 Oct 2026).
3. GOV.UK, "Late commercial payments: Interest on late commercial payments". gov.uk (accessed 16 Oct 2026).