What legally has to be on an invoice

There is no single global rule, and most "invoice checklist" articles blur several countries together. Here is what the UK, the EU, Canada, and the US actually require, each linked to its official source so you can verify it. Then you can create a compliant invoice in about a minute.

United Kingdom

If you are not VAT-registered, an invoice is light: clearly mark it "invoice," and show your business name and contact details, the customer's name and address, a description of what you're charging for, the date, and the amount.^[1]

If you are VAT-registered, a full VAT invoice must additionally include a unique sequential invoice number, your VAT registration number, the tax point (date of supply), the unit price and quantity per item, the VAT rate charged on each item, the total excluding VAT, the total VAT, and the amount including VAT. Invoices under £250 can use a simplified format.^[1]

European Union

The EU harmonises invoice content in Article 226 of the VAT Directive (2006/112/EC), which sets an exhaustive list of mandatory particulars. Key items: the date of issue; a sequential number that uniquely identifies the invoice; the supplier's VAT identification number (and the customer's, in certain cross-border cases); the full name and address of both supplier and customer; the quantity and nature of the goods or services; the date of supply; the taxable amount per VAT rate; the VAT rate applied; and the VAT amount payable.^[2]

Canada (GST/HST)

The Canada Revenue Agency ties requirements to the sale amount, so your customer can claim input tax credits:^[3]

United States

There is no federal law mandating an invoice format. You invoice according to your contract and normal business practice. For taxes, the IRS requires you to keep records that support the income and deductions on your return, but it does not prescribe specific invoice fields.^[4] Note that sales tax is administered by each state, and some states require sales tax to be stated separately on the receipt or invoice, so check your state's rules if you collect it.

The safe default (works everywhere)

Include all of these and you'll satisfy the common core across jurisdictions:

• The word "Invoice" and a unique, sequential invoice number
• Your business name, address, and tax/VAT/GST number if you have one
• The client's name and address
• Issue date (and tax point / supply date where relevant)
• A clear description, quantity, and unit price per line
• Tax rate and tax amount shown separately, and the total
• Payment terms and a due date

Billfold builds an invoice with all of these by default — sequential numbering, per-line tax, separate tax totals, and terms — so a compliant invoice is the starting point, not a checklist you have to remember.