Why an invoice requirements checklist matters
An invoice requirements checklist is the difference between an invoice that gets paid in 14 days and one that bounces around an accounts payable inbox for two months. The work was done. The amount is correct. But one missing field — a VAT number, a PO reference, the words "Tax Invoice" at the top — is enough for an automated AP system or a careful tax authority to push it back.
The cost is real. Around 85% of freelancers report being paid late at some point, and a meaningful share of those delays trace back to invoice elements that weren't on the document. Worse, in VAT and GST regimes a non-compliant invoice doesn't just slow payment — it stops the client from reclaiming the tax, which makes you the source of their problem.
This checklist gives you a region-aware audit before the invoice goes out. It covers what should be on an invoice in the US, UK, EU, Australia, and Canada, splits each item into required vs recommended for that regime, and produces a plain-text summary you can save with your project notes.
Region-by-region summary of invoice requirements
United States
There's no federal invoicing law in the US. State sales tax rules and the procurement policies of your client's accounts payable team are the binding constraints. A defensible US invoice includes your business name and address, your client's full legal name and billing address, a unique invoice number, issue and due dates, itemized line descriptions with quantity and rate, a subtotal, a separate sales tax line if you're collecting it, the grand total, and your payment instructions. Including your EIN is recommended for B2B work — many enterprise vendor portals require it before they cut a check.
United Kingdom (HMRC, VAT-registered)
HMRC requires a full VAT invoice for any taxable supply over £250, with simplified invoices allowed below that. The full invoice must show: a unique sequential number; your business name, address, and VAT registration number; the customer's name and address; the date of supply (tax point); the invoice date; a description of the goods or services; the VAT rate applied per line item (20% standard, 5% reduced, or 0%); the net, VAT, and gross totals; and the unit price for each line. If any items are at different VAT rates, that has to be clear on the invoice. These rules are the reason a UK VAT invoice has so many more fields than a US invoice for the same job.
European Union (Directive 2006/112/EC)
The EU's harmonised VAT invoicing rules sit in Council Directive 2006/112/EC, with content requirements in Article 226. A full EU VAT invoice must include the issue date, a sequential invoice number, your VAT identification number and the customer's VAT number where applicable, both parties' full names and addresses, the quantity and nature of the supply, the date of supply, the unit price, the VAT rate, the VAT amount per rate, and the total amount payable. Simplified invoices are permitted for amounts under €100 (with member state variations up to roughly €250), and the EU is moving to mandatory structured e-invoicing for B2B from 2028.
Australia (ATO)
If you're GST-registered and selling more than A$82.50 (GST inclusive), Australia's ATO requires you to issue a tax invoice when the customer asks. The invoice must show the words "Tax Invoice" prominently, your Australian Business Number (ABN), the issue date, a brief description of the items including quantity and price, and the GST amount payable — either on its own line or as the statement "Total price includes GST" if the GST is exactly 1/11 of the total. For sales of A$1,000 or more you also have to show the buyer's identity or ABN. The ATO requires you to keep tax invoice records for five years.
Canada (CRA)
The CRA scales documentation requirements with the invoice value. Under C$30 you only need the supplier name, date, and total. Between C$30 and C$150 you also need your GST/HST registration number and payment terms. Above C$150 the CRA requires the buyer's name, itemised descriptions, and the tax amount shown separately. Tax should always be displayed separately from the net price, and the GST or HST rate should match the customer's province (HST 13% Ontario, GST 5% Alberta, and so on). Records must be kept for six years from the end of the tax year.
What AP teams actually look for
Tax law is one filter. The accounts payable team is the other, and they reject more invoices than the tax authority ever will. From procurement guidance and freelance forums, the recurring pattern is the same: missing PO number, mismatched legal entity name, vague line descriptions ("services rendered"), no payment instructions, wrong currency, and inconsistent invoice numbering. None of those are illegal. All of them stop payment.
The fix is to treat the AP team as a co-author of the invoice format. Ask before the first invoice: do you require a PO number, what legal entity should I bill, where do I send the invoice, and what payment terms apply. The five minutes that conversation costs is the cheapest insurance you can buy against a 45-day delay.
Common reasons invoices get rejected
Across the search results and freelancer reports, the same handful of reasons keep coming back:
- The invoice is missing the PO number or has the wrong one.
- The supplier's tax ID (EIN, VAT number, ABN, GST number) is missing.
- The client's legal name on the invoice doesn't match what's in their AP system.
- Line descriptions are too vague to map to the contract or PO.
- Sales tax, VAT, or GST is not shown as a separate line.
- There's no due date, or the terms aren't clear.
- The currency isn't stated and a "$" symbol is ambiguous.
- The bank details or payment link aren't on the invoice.
The audit checklist above maps directly to that list. If every required item for your region is checked, you've removed the most common reasons an invoice gets sent back.
The difference between an invoice and a tax invoice
An "invoice" is a generic commercial document — a request for payment with enough detail that both parties agree what's owed. A "tax invoice" or "VAT invoice" is a regulated document that triggers the buyer's right to reclaim input tax. The difference matters because tax invoices have mandatory fields, mandatory wording (the literal phrase "Tax Invoice" in Australia, for example), and statutory retention periods. Issue a regular invoice when you should have issued a tax invoice and you've created a problem your client can't fix without your help.
If you're VAT-registered in the UK or EU, GST-registered in Australia, or GST/HST-registered in Canada, default to issuing tax invoices for every business sale. The checklist above defaults to tax-invoice rules whenever you select one of those regions, so you don't have to remember which fields move from optional to required.