Most late payments do not start with a client who refuses to pay. They start with an invoice that cannot be processed. The PO number is missing, so it sits in a queue. It is addressed to the marketing manager instead of the company, so accounts payable cannot match it. The bank details are in last month's email, not on the invoice. Each of these adds a week, and none of them is the client's fault.
This checklist is a one-minute pre-send check. Run through it before every invoice and most of those delays disappear.
TL;DR
The invoice checklist covers what every invoice must contain before you send it: the word invoice, a unique sequential number, issue and due dates, your legal details and tax ID, the client's legal entity, PO reference, specific line items, tax at [TAX RATE]% where you charge it, total due, payment methods, and the right recipient. Run it before every send. Wrong billing entity and missing PO numbers are the most common reasons invoices get stuck.
What's inside
- Identity — invoice label, number, dates, your legal details, client legal entity.
- References — PO, contract or SOW, project name, billing period.
- Content — line items, quantities, rates, deposits credited, expenses with receipts.
- Money — subtotal, discount, tax, total, currency.
- Payment — due date, terms, methods, reference to quote, fee instructions.
- Delivery — recipient, subject line, attachments, follow-up date.
- After sending — record it, set a reminder, track payment.
When to use it
Use it before sending any invoice: deposits, milestones, retainers, hourly invoices and final balances. It is particularly useful when invoicing a new client for the first time, a large company with procurement processes, or an international client.
If you need a ready-made invoice layout rather than a checklist, start from the freelance invoice template. If you find an error after sending, do not edit and resend; issue a credit note. If the invoice is already late, the payment reminder emails give you a polite sequence.
The five things that delay payment most
Wrong billing entity. Invoices go to legal entities, not people. "Acme Holdings Ltd" pays; "Sarah in marketing" does not. Ask for the exact billing name and address during onboarding.
Missing PO number. Many larger companies cannot pay any invoice without a matching purchase order. Ask before you invoice, not after it bounces.
Vague line items. "Services rendered" forces the approver to ask what was done. Name the deliverable or period.
No payment instructions. Put the bank details or payment link on the invoice itself, every time.
Wrong recipient. Your day-to-day contact often forwards invoices late or not at all. Send to the accounts payable address and copy your contact.
The how to get clients to pay invoices on time post covers payment terms and reminders in more depth.
The first invoice to a new client
The first invoice is where most problems surface, because you do not yet know how the client's finance team works. Ask three questions during onboarding: the exact billing entity and address, the accounts payable email, and whether they need a PO or supplier setup. The body of this checklist includes a short section for first invoices.
Legal requirements vary
What an invoice legally must contain depends on where you are registered and whether you charge sales tax, VAT or GST. Some countries require specific wording, sequential numbering, or both parties' tax IDs on business invoices. This checklist covers the common ground; confirm the specifics for your country with your tax authority's official guidance or an accountant.
Customize it in your COLO workspace
COLO invoices include line items, tax rates, discounts and per-customer or per-document currency, and you can email the invoice from COLO or download a PDF. Partial payments are recorded against the invoice, and clients can pay by card through Stripe or by PayPal from the client portal, so the payment link is always attached to the invoice itself. See Invoicing and Payments.
Why this template works
- It is short enough to run every time. One minute before sending.
- It targets the common delays. Entity, PO, line items, payment details, recipient.
- It separates legal from practical. You confirm local rules once, then reuse them.
- It includes what happens after sending. A reminder date is part of the invoice.
FAQ
Q: What must be on an invoice?
Common essentials are the word invoice, a unique invoice number, issue date, your legal name and address, the client's legal name and address, a description of the work, amounts, tax if charged, total due, due date and how to pay. Some countries require more, such as tax IDs.
Q: Why do invoices get rejected by accounts payable?
The most common reasons are the wrong legal entity, a missing PO number, missing tax IDs, amounts that do not match the PO, or the invoice going to the wrong email address.
Q: Do I need a tax ID on my invoice?
If you are registered for sales tax, VAT or GST, many countries require your registration number on the invoice. Some cross-border business invoices also need the client's tax ID. Check your local tax authority's guidance.
Q: Can I reuse or skip invoice numbers?
Do not reuse numbers. Many tax systems expect a continuous sequence. If you need to cancel an invoice, issue a credit note rather than deleting it or reusing the number.
Q: How should I send an invoice?
Send it to the billing address the client gave you, usually an accounts payable email, with the invoice number in the subject line and a PDF attached or a payment link included.