Invoice Requirements by Country: US, UK and EU Basics
Not legal advice: this is general educational information about invoicing requirements. Tax law changes and has edge cases — verify anything critical with an accountant or the relevant tax authority.
Invoicing rules differ more than most small businesses expect. What's a polite formality in one country is a legal requirement in another — and getting it wrong can mean rejected input-tax claims for your client or penalties for you. Here are the basics for the three regimes you're most likely to encounter.
United States: flexible, but keep records
The US has no federal law dictating invoice format the way the EU does. There's no mandated invoice template, no required invoice number sequence at the federal level, and no VAT-style invoice content rules. That flexibility is deceptive, though — you still need:
- Clear identification of seller, buyer, goods/services, amounts, and dates — the IRS expects your records to substantiate every dollar of reported income.
- Sales tax handling where applicable: whether you must charge it depends on nexus (your connection to the buyer's state) and the type of sale. When you do charge it, show it as a separate labeled line.
- Sequential numbering isn't federally required but is strongly recommended — gaps and duplicates raise questions in any audit.
- Record retention: the IRS generally expects you to keep records for at least 3 years from the filing date (longer in cases of substantial understatement).
Bottom line for the US: the law cares less about the invoice's appearance and more about whether your records prove the income. Be thorough anyway — your clients' accountants will thank you.
United Kingdom: VAT invoices have strict rules
If you're UK VAT-registered, your invoices must meet HMRC's requirements. A valid VAT invoice needs:
- A unique, sequential invoice number
- Your business name, address, and VAT registration number
- The customer's name and address
- Description of goods/services, quantity, and rate
- The tax point (time of supply) — usually the invoice date, but it can differ
- VAT rate applied and VAT amount per rate, plus the total including VAT
- For invoices over £250, additional details apply (full VAT invoices vs. simplified invoices under £250 have different thresholds)
Non-VAT-registered businesses have lighter requirements but must not show VAT on invoices or imply they're VAT-registered. Keep records for at least 6 years.
European Union: the most detailed requirements
EU VAT invoicing rules (under the VAT Directive) are the strictest of the three. A compliant EU invoice generally must show:
- Sequential invoice number (no gaps)
- Issue date
- Supplier's name, address, and VAT identification number
- Customer's name, address, and VAT number (for intra-EU B2B supplies)
- Full description of goods/services
- Taxable amount per VAT rate, the VAT rate, and the VAT amount payable
- For intra-EU B2B supplies: the reverse charge note ("Reverse charge") instead of charging VAT
- References to exemptions where applicable (with the legal basis)
Many EU countries are also rolling out mandatory e-invoicing for B2B transactions on staggered timelines — if you invoice EU business clients regularly, check the current status for the specific countries involved. Our e-invoicing guide covers what this means in practice.
Record retention is typically 7–10 years depending on the member state — longer than the US or UK.
Side-by-side comparison
- Strictness: EU (most detailed) → UK (detailed for VAT) → US (flexible, records-focused)
- Sequential numbering: effectively required in EU/UK; recommended in US
- Tax ID on invoice: required in EU/UK VAT invoices; not a US federal concept
- Record keeping: US ~3+ years, UK 6 years, EU 7–10 years
- E-invoicing mandates: advancing fastest in the EU; limited in US/UK so far
What to do in practice
- Identify your regime: where are you established, where are your clients, and are you tax-registered?
- Use the strictest applicable standard as your default template — an invoice that satisfies EU rules will satisfy US expectations too.
- Always use sequential numbering regardless of jurisdiction.
- Show taxes as separate labeled lines with rates — universal good practice.
- Keep every invoice for at least the longest retention period that applies to you.
- Revisit annually: thresholds change, e-invoicing mandates expand, and your client mix evolves.
Key takeaways
- The US is flexible on format but strict on records; the EU is strict on both.
- UK/EU VAT invoices require VAT numbers, sequential numbering, tax points, and per-rate VAT amounts.
- Intra-EU B2B supplies generally use reverse charge — don't charge VAT, add the required note.
- Default to the strictest standard that applies to you; keep records for the longest required period.
- This is general information — confirm specifics with a professional for your situation.