Question 1

What is legally required on an invoice?

Accepted Answer

It depends on your country and tax status. In the US there's no federal invoicing law — you need clear identity, an invoice number, dates, line items, totals, and payment terms. In the UK, EU, Australia, and Canada, if you're registered for VAT or GST you must add your tax registration number, the tax rate (per line in the UK and EU), and the tax total. Pick your region in the checklist above to see the exact required fields.

Question 2

Is a US invoice the same as a tax invoice?

Accepted Answer

No. In the US, an 'invoice' is a generic billing document and there's no statutory format. In Australia, the UK, and the EU, a 'tax invoice' or 'VAT invoice' is a specific document with mandatory fields that lets the buyer reclaim input VAT or GST. If you're billing an Australian or UK client and you're tax-registered, you need to issue a tax invoice, not just a regular invoice.

Question 3

What is a VAT invoice?

Accepted Answer

A VAT invoice is the document a VAT-registered business issues for taxable supplies. In the UK, a full VAT invoice must include a unique number, your VAT registration number, the date of supply, the customer's name and address, a description of the goods or services, the VAT rate per line, and the net, VAT, and gross totals. The EU equivalent is set out in Article 226 of Council Directive 2006/112/EC.

Question 4

Do I need a PO number on my invoice?

Accepted Answer

Only if your client uses purchase orders — but if they do, you absolutely need it. Most enterprise accounts payable systems do an automatic three-way match between PO, goods receipt, and invoice. No matching PO means the invoice is rejected before a human ever sees it. Always ask for the PO number before you start the work, not after.

Question 5

What happens if my invoice is missing required information?

Accepted Answer

Best case: the client's AP team sends it back and asks you to reissue, costing you days or weeks. Worst case: in VAT or GST regimes, the client cannot reclaim the tax and the invoice fails a tax audit, exposing both sides to penalties. The checklist above flags every required field for your region so this doesn't happen.

Question 6

Do I need to put my address on an invoice?

Accepted Answer

Yes, in almost every region. AP teams use it to verify you're a real vendor, and tax authorities use it to confirm the supplier is who you say you are. A PO box alone is often refused — use a real street address (your registered business address or home address if you're a sole proprietor).

Question 7

Do I need an invoice number if I'm a freelancer?

Accepted Answer

Yes. Every invoice should have a unique, sequential invoice number with no gaps. AP teams use the number to spot duplicates, and tax authorities expect it for reconciliation. A simple format like 2026-001, 2026-002 works fine — what matters is that no two invoices share the same number.

Question 8

How long do I need to keep invoices?

Accepted Answer

It varies. The US IRS expects three years generally, six or seven in some cases. UK HMRC requires VAT invoices for six years. EU member states typically require ten years. Australia's ATO requires five years, and Canada's CRA requires six years from the end of the tax year. Save a copy of every invoice and the checklist summary alongside it.

Invoice Compliance Checklist

Identity

Document

Line items

Totals

Payment

Status