Most late payments aren't about money. The client fully intends to pay, but the invoice is stuck: sent to the wrong person, missing a purchase order number, or describing the work so vaguely that the approver doesn't recognise it. It sits in someone's inbox until you chase it.
An invoice that gets paid on time is one that's easy to approve. This is the checklist we built Branded Invoices around, and it applies however you produce your invoices.
The checklist
| Part | What to include | Why it matters |
|---|---|---|
| Your details | Business name, address, email, tax registration number | Identifies the supplier; tax numbers are often required |
| Client details | Legal entity name, billing address, contact or department | Invoices to the wrong entity get sent back |
| Invoice number | Unique and sequential, e.g. INV-1042 | Referencing, matching payments, audit trail |
| Dates and terms | Issue date, due date, terms such as Net 30 | Starts the payment clock |
| Client references | Purchase order, project code, contract number | Many clients can't approve without one |
| Line items | Description, period, quantity, rate, amount | What the approver actually reads |
| Totals | Subtotal, each tax shown separately, total and currency | Accounts payable checks the arithmetic and tax |
| How to pay | Payment link, bank details, accepted methods | Every extra step delays payment |
What goes in each part
Your details and tax number
Your business name as it's registered, a contact email, and your sales tax, GST, HST or VAT registration number if you're registered. In many places the registration number has to appear on the invoice for the client to claim the tax back. Rules differ by country and region, so check what applies to you.
The client's legal entity
Not the brand name, not the person who hired you: the legal entity that pays. Larger clients often have several companies, and an invoice addressed to the wrong one will be rejected, usually weeks later.
Number, dates and terms
A unique, sequential invoice number, the issue date and a due date. Write the due date out rather than relying on "Net 30" alone. Approvers check dates, not arithmetic.
Client references
If the client gave you a purchase order number, it goes on every invoice. Ask for one at the start of the engagement. For a lot of companies, no PO means no payment, however good the work was.
Line items
This is where most invoices fall short. "Consulting services: $4,000" makes the approver go and ask someone. "Pricing strategy workshop, October 8 (agreed fixed fee)" gets approved. Each line should say what was done, for which period, and how it was priced: a fixed fee, a quantity of hours or units, or a milestone.
Totals and tax
Subtotal, each tax shown on its own line with its rate, and the total with its currency. If you bill across borders or in more than one currency, state the currency on every invoice, not just on the first one.
How to pay
A payment link the client can use by card or bank transfer is the fastest. Bank details work too. Invoice fraud often works by sending a convincing invoice with changed bank details, so if yours ever change, tell clients separately and expect them to check.
What clients actually check
Someone in accounts payable will look at your invoice for under a minute. In that minute they check:
- Is it addressed to us? The right legal entity and address.
- Is there a PO, and does it match? Number, and often the remaining amount on the PO.
- Do we recognise it? A description the budget holder will approve without a meeting.
- Does it match what we agreed? Rate, fee or estimate from the engagement letter or statement of work.
- Is the tax right? The rate, and your registration number where they need it.
- Is it a duplicate? A unique number and a clear period make that easy to rule out.
- Have the bank details changed? If they have, it gets held.
A worked example
Here's an invoice from a fictional consultancy, Fernhill Advisory, to a client, Larch Street Bakery Ltd., in Ontario, where HST is 13%.
| Description | Qty | Rate | Amount |
|---|---|---|---|
| Pricing strategy workshop, October 8 (fixed fee per SOW-07) | 1 | $2,400.00 | $2,400.00 |
| Follow-up advisory, October 9–31 (hours, see attached log) | 6 | $175.00 | $1,050.00 |
| Subtotal | $3,450.00 | ||
| HST 13% (registration no. on invoice) | $448.50 | ||
| Total due (CAD) | $3,898.50 |
Above the lines: invoice INV-1042, issued October 31, due November 30 (Net 30), PO 4471 from Larch Street Bakery Ltd. Below: a payment link for card or bank transfer. The approver can tick every item on the list above without asking anyone a question.
Common mistakes
- Vague descriptions. "Services rendered" gets queried.
- No PO number. Ask for it up front, and put it on every invoice.
- Combining periods. One invoice per period or milestone keeps disputes small.
- Reusing or skipping numbers. It makes duplicates and gaps hard to explain.
- Sending to the person, not the process. If the client has an accounts-payable address, use it, and copy your contact.
- Making it hard to pay. A PDF with no payment link and no bank details is a request to wait.
Once invoices are going out, the next job is getting them into the books without retyping them. QuickBooks Online and Xero can both import invoices from a CSV, as long as the file is laid out the way they expect.
Frequently asked questions
What must a professional services invoice include?
At minimum: your business name and contact details, the client's legal name and address, a unique invoice number, the issue date, the due date or payment terms, a description of the services with quantities and rates, the subtotal, any sales tax, GST, HST or VAT shown separately with your registration number where required, the total and how to pay. Requirements vary by country and region, so check local rules.
Why do clients reject or delay invoices?
The most common reasons are a missing or wrong purchase order number, the wrong legal entity, a description too vague to approve, a rate or amount that doesn't match the engagement letter, and missing tax details. Large clients' accounts-payable teams often send these back without telling the person who hired you.
Should invoice numbers be sequential?
Yes. A unique, sequential number makes each invoice easy to reference and to find in your books, and many tax authorities expect invoices to be numbered in a way that shows none are missing. A prefix such as INV- is fine.
Should I bill in advance or in arrears?
Fixed-fee and retainer work is usually billed in advance, at the start of the month or milestone. Hourly work is usually billed in arrears, after the hours are worked. Whichever you use, say which period the invoice covers.