An invoice isn't just a request for payment — in most countries, it's a legal and tax document. Missing the wrong field can mean a client's accountant rejects it, or it can create problems for you when you file taxes. Here's the full checklist of what a legally sound invoice actually needs.
The Non-Negotiable Fields
Nearly every tax jurisdiction requires these on a valid invoice:
- The word "Invoice" — clearly labeled, not just implied
- A unique invoice number — sequential, never reused
- Issue date — the date the invoice was created
- Seller's legal name and address — matching your registered business details
- Buyer's name and address — the client being billed
- Description of goods or services — specific enough to justify the charge
- Total amount due — clearly stated, including currency
Tax-Specific Requirements
If you charge VAT or sales tax, additional fields typically apply:
- Your VAT/tax registration number — required in most VAT-based tax systems
- Tax rate applied — shown as a percentage (e.g., 20%)
- Tax amount — the actual currency value of tax charged, shown separately from the subtotal
- Net and gross totals — before and after tax, listed individually
Cross-border note: If you're invoicing a client in another country, tax rules can shift significantly — some transactions are zero-rated, others require the client's VAT number on the invoice itself. When in doubt, check the rules for both your country and the client's.
Fields That Aren't Legally Required — But Should Be There Anyway
- Due date — not always mandatory, but omitting it is the single biggest cause of late payment
- Payment terms — Net 15, Net 30, due on receipt, etc.
- Accepted payment methods — bank transfer, PayPal, card
- Late payment policy — if you charge interest or fees on overdue invoices, state it here, not after the fact
What Happens If a Field Is Missing?
Consequences range depending on what's missing and where you operate:
- A client's accounting department may reject the invoice outright and ask for a corrected version — delaying payment by days or weeks
- Missing tax fields can mean the client can't reclaim VAT, which damages the business relationship
- In an audit, incomplete invoices can be disallowed as valid expense records — a problem for both sides
Quick self-check: Before sending, ask yourself — could a stranger look at this invoice and know exactly who's being billed, for what, how much, and by when? If yes, you've covered the essentials.
Want to see how these fields fit together in practice? Our step-by-step invoice guide walks through building one from scratch.
Every required field, filled in automatically — free, no sign-up.
CREATE A COMPLIANT INVOICE →