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What has to be on an invoice, and what the law adds

The nine things every invoice needs, then what the UK, the EU, the US, India and Australia add on top. Each rule sourced from the tax authority itself.

By Harish11 October 20264 min read

Every invoice needs nine things: a unique number, the date you issued it, your name and address, your client’s name and address, what you did or sold, when you did it, how much each part costs, any tax, and the total they owe. Everything else is either a legal addition that depends on where you are and whether you are registered for VAT or GST, or a courtesy that gets you paid faster.

That first list is close to word for word what HMRC asks of a UK business that is not registered for VAT, and it works as a floor almost everywhere. The rest of this post is about what sits on top of it.

The nine things, and why each one is there

An invoice is two documents at once. For your client it is a request for money. For both of your accountants it is a record that a sale happened, on a date, for an amount. Every field on the list exists for one of those two jobs.

Field	Why it is there
Invoice number	So both sides can refer to this one bill and no other. It is also how an auditor spots a missing invoice. There is a whole post on how to number invoices.
Issue date	Starts the clock on payment terms, and decides which tax period the sale falls in.
Your name, address and contact details	Who is owed. For a limited company in the UK this means the full registered name.
Client’s name and address	Who owes it. Accounts teams file invoices by this, so use their legal name, not the name of the person you emailed.
Description	What was supplied. “Consulting” is weak. “Website copy, 12 pages, delivered 14 September” survives a dispute.
Supply date	When the work was done or the goods delivered, if that is not the issue date.
Amounts	What each line costs. Quantity times rate, so the client can check the arithmetic.
Tax	The rate and the amount, if you charge any.
Total due	The one number the reader is looking for.

Two more are not legally required anywhere we checked, and belong on every invoice anyway: a due date and how to pay you. An invoice that does not say when or where to pay is a request with no instructions. We cover due dates, “Net 30” and what the law says when a client pays late in invoice payment terms.

What changes once you are registered for VAT or GST

This is the dividing line. A freelancer below the registration threshold is writing a commercial document. A registered business is writing a tax document, one the client will use to reclaim the tax you charged, and so the tax authority says exactly what must be on it.

The table below is the extra, on top of the nine things. Each row comes from the authority’s own page, linked under Further reading.

Where	Who it applies to	What it adds
UK	VAT registered businesses (VAT Notice 700, section 16)	Your VAT registration number. The time of supply (the tax point). For each line: quantity, VAT rate and the amount excluding VAT, plus the unit price. The total excluding VAT, and the total VAT in sterling.
EU	VAT registered businesses (VAT Directive, Article 226)	Your VAT number, and the client’s too where they account for the VAT (for example under reverse charge). Taxable amount per VAT rate, unit price excluding VAT, the rate and the VAT amount. Specific wording where it applies: “Reverse charge”, “Self-billing”, or a reference to the exemption you are using.
US	Everyone	Nothing at federal level. The IRS says that “except in a few cases, the law does not require any specific kind of records”. Invoices are named as supporting documents, and state sales tax rules may add to that.
India	GST registered businesses (CGST Rules, rule 46)	Your GSTIN and the client’s if registered. The HSN or service code. Taxable value, rate and amount of each of CGST, SGST, IGST or UTGST. Place of supply for sales between states. Whether reverse charge applies. A signature, unless the invoice is electronic.
Australia	GST registered businesses (ATO, tax invoices)	Words showing the document is intended to be a tax invoice. Your ABN. The GST amount, or the line “Total price includes GST” when GST is exactly one eleventh of the total. For sales of A$1,000 or more, the buyer’s identity or ABN as well.

A few details that surprise people:

Smaller sales can use a shorter invoice. In the UK a simplified VAT invoice is allowed when the supply is £250 or less and the customer agrees. Across the EU, member states must allow one up to €100, and may allow it up to €400.
In Australia you do not have to issue a tax invoice unprompted for small sales. If a customer asks for one you must provide it within 28 days, unless the sale was A$82.50 including GST or less.
The EU list is about to change. The “VAT in the Digital Age” package amends Article 226 from July 2030, as part of the move to structured electronic invoices. The list above holds until then.

The part nobody tells freelancers

If you are not registered for VAT or GST, do not put a tax line on your invoice. It is tempting to add one because the big companies do, but charging tax you are not registered to collect is a far bigger problem than leaving a field blank. A zero rate line is fine. An invented one is not.

Billing a client abroad, or in a currency other than your own, brings its own questions: which exchange rate to use, and which currency the tax has to be shown in. Those have their own post.

How our generator maps to this

We would rather you know the gaps before you find them. Our invoice has a field for every one of the nine things, plus a due date and a notes box for payment details. Your name, address and tax number go in the details block under your business name, and are kept for next time.

What it does not do yet:

One tax rate per invoice. Enough for most freelancers. Not enough for an invoice that mixes standard and reduced rate items, which should go out as two invoices until that changes.
No separate supply date or HSN column. Put the supply date in the line description (“Design work, 1 to 14 September”), and the HSN or SAC code there too.
The heading always says “Invoice”. Australian businesses registered for GST should add “Tax invoice” to the notes so the document states its purpose.
Tax is worked out once, on the subtotal, and rounded to the nearest cent. That can differ by a penny from a client whose system rounds each line, and HMRC allows a VAT total to be rounded down rather than to the nearest penny. The detail is in why your invoice total is off by a cent.