An invoice is two documents at once. For your customer it is a request for payment; for a tax authority it is the evidence behind the tax you charged and the tax your customer will reclaim. Most invoice templates are designed for the first job and quietly fail the second. The checklist below is built from the rules that VAT and GST countries actually write down — the EU's VAT Directive, the UK, the Gulf states, Australia and others — and it is a sensible standard even where no law requires it.
The 14-point checklist
| Field | Why it is there |
|---|---|
| 1. The word "Invoice" (or "Tax invoice") | Distinguishes it from a quote or a delivery note. Several VAT countries require the exact words "Tax invoice". |
| 2. A unique, sequential number | Required almost everywhere. Gaps and reused numbers are the first thing an auditor looks for. |
| 3. Issue date | Starts the payment term and usually decides the tax period. |
| 4. Date of supply, if different | Where goods were delivered or work done in a different period, the supply date can decide when tax is due. |
| 5. Your legal name and address | As registered — not just a trading name. |
| 6. Your tax registration number | VAT, GST or TRN number, wherever you are registered. |
| 7. Customer's name and address | Identifies who owes the money and who may reclaim the tax. |
| 8. Customer's tax number (business sales) | Needed for cross-border and reverse-charge sales in the EU, and for business customers in many other VAT systems. |
| 9. Description of goods or services | Specific enough that a third party could tell what was sold. |
| 10. Quantity and unit price | Per line, before tax, with any discount shown separately. |
| 11. Tax rate and tax amount per rate | Including 0% and exempt lines, with the reason where the rate is not standard. |
| 12. Totals: net, tax, gross | Three numbers that must add up, to the currency's own decimal places. |
| 13. Currency (and tax in local currency) | A foreign-currency invoice often still has to state the tax in the local currency. |
| 14. Payment terms and how to pay | Due date and bank or payment-link details. The single biggest driver of getting paid on time. |
The three habits behind most invoice problems
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Editing an invoice after it was sent
Once a customer has an invoice, it is a record. Changing the amount on the same number means your books and theirs now disagree. Issue a credit note against the original and, if needed, a new invoice.
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Deleting or reusing numbers
A cancelled invoice keeps its number and is voided, not deleted. A gap in the sequence is a question you will be asked to answer.
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Rounding the tax by hand
Tax worked out per line and then per invoice can differ by a cent. Pick one method, apply it everywhere, and let the software do it.
Electronic invoicing is changing the format, not the content
A growing number of countries — Saudi Arabia, the UAE from 2027, Italy, France, Poland, India and many in Latin America — now require business invoices to be issued as structured data and reported or cleared with the tax authority. The fields above do not change; what changes is that a missing one is rejected by a machine in seconds instead of found by an auditor years later. An invoice process that already gets the checklist right is most of the way to e-invoicing.
Questions people actually ask
Do I need a separate invoice number series for each customer?
No. One continuous series for the business is the norm. Some countries allow separate series (for example per branch), provided each one is sequential and identifiable.
Can I correct a mistake on an invoice I already sent?
Not by editing it. Issue a credit note that references the original invoice, then a new, correct invoice. That way both sets of books stay in agreement and the audit trail is complete.
How long should I keep invoices?
It depends on the country — commonly between five and ten years. Check your own tax authority's record-keeping rule and keep electronic copies for at least that long.
Is a PDF invoice an e-invoice?
Not in the legal sense used by e-invoicing mandates. Those require structured data (such as UBL XML) exchanged through an approved channel. A PDF is still fine wherever no mandate applies.
Where these facts come from
Checked against the following on 15 October 2026. Rules and dates change — if you are reading this long after that date, verify before you act on it.
- EU VAT Directive 2006/112/EC, Article 226 — invoice contents
- GOV.UK — Invoicing and taking payment from customers
- Australian Taxation Office — Tax invoices
WisoBooks is a bookkeeping and business-management tool, not an accounting, tax or legal advisor. Nothing on this page is tax advice, and tax rules change. Confirm your own obligations with the relevant authority or a qualified advisor.
