An invoice is a commercial document, and in most jurisdictions it is also a tax document. Getting the contents right matters for two separate reasons: your own compliance, and your client's ability to actually process the payment.
#The universal elements
These appear in essentially every jurisdiction's requirements:
The word "Invoice." It distinguishes the document from a quote, a proforma or a statement. Finance teams route documents by type, and an untitled one gets misrouted.
A unique sequential number. Tax authorities generally require an unbroken series so that missing numbers cannot conceal unreported revenue. Never delete or reuse a number — issue a credit note instead.
Issue date. The date the invoice is raised, which usually determines the tax period it falls into.
Your business details. Trading name, legal name if different, address and contact details. Where you operate as a limited company, most jurisdictions require the registered company number and registered office address.
Your tax registration number. Where you are registered for VAT, GST or sales tax, this is mandatory. Without it your client cannot reclaim input tax.
The client's name and billing address. Their legal entity name, not the trading name or your contact's name. Getting this wrong is a common reason invoices are rejected.
A description of goods or services. Specific enough that a third party could understand what was supplied. Quantity and unit price per line.
Amounts. Subtotal, tax charged shown separately with the rate applied, and the total due.
Due date and payment terms. Explicit, as a calendar date.
#Country-specific additions
United Kingdom. VAT-registered businesses must show the VAT number, the tax point (supply date) where it differs from the issue date, the rate applied per line, and the total VAT in sterling. Limited companies must show the registered company number and registered office.
European Union. Similar VAT requirements, plus for cross-border B2B supplies both parties' VAT numbers and a note that the reverse charge applies.
United States. There is no federal invoice format requirement, since there is no VAT. Sales tax obligations vary by state and depend on nexus. Practical requirements are driven mainly by your client's accounts payable process rather than by law.
India. GST invoices have prescribed contents including GSTIN for both parties, HSN or SAC codes, place of supply and a compliant serial number.
Canada. GST/HST registrants must show the registration number, and the required detail increases with the invoice value.
Where you sell across borders, the rules of the customer's jurisdiction frequently govern. Check before assuming your home format is sufficient.
#The omissions that actually stop payment
Legal validity and getting paid are related but different. These are the practical blockers:
No purchase order reference. In many mid-size and large companies an invoice without a matching PO cannot be entered into the system. It is not rejected with an explanation; it simply sits.
Wrong legal entity. Invoicing "Northwind" when the contracting entity is "Northwind Trading Company Limited" fails a three-way match and stops the payment.
Bank details incomplete. Missing IBAN, missing SWIFT/BIC on an international payment, or no reference instruction all result in a payment that cannot be made or cannot be reconciled.
Description that does not match the contract. If the statement of work listed three deliverables and the invoice describes something else, an approver has to investigate rather than approve.
#Numbering that survives an audit
Use an unbroken sequence. Practical schemes:
2026-001,2026-002— year prefix, resets annuallyINV-1041— single running series across all yearsACME-007— client-coded, useful with a few large accounts
Keep a record of every number issued, including cancelled ones. If an invoice is raised in error, issue a credit note referencing the original rather than deleting it — a gap in the sequence is exactly what an auditor looks for.
#Storage and retention
Most jurisdictions require invoices to be retained for five to seven years, and increasingly accept electronic copies provided they are complete and unaltered. Keep both the PDF you sent and the underlying record.
The invoice generator includes every universal field, computes tax per line and produces a print-ready PDF with your branding. Nothing is uploaded — the document is rendered on your device, which matters given it contains your client's details and your bank information.
Frequently asked questions
Does an invoice need a signature?
Generally no. Invoices are not contracts and do not require signing in most jurisdictions. A few countries and some specific B2G processes require signed or digitally certified invoices, so check locally if you supply government bodies.
What is the difference between an invoice and a receipt?
An invoice requests payment for goods or services supplied. A receipt confirms payment has been made. They serve different accounting purposes and both may be needed for the same transaction.
Can I invoice in a foreign currency?
Yes. Invoice in the currency stated in your contract. If you are VAT or GST registered, most jurisdictions require the tax amount also to be shown in your home currency at a specified exchange rate.