What has to be on an invoice, and what just helps you get paid

There are two separate questions about an invoice, and mixing them up is why so many templates are both over-designed and missing something.

The first is what has to be on it. That is a short, settled list. The second is what makes someone actually pay it, which is not the same list and is not written down anywhere official.

#The nine things GOV.UK requires

From Invoicing and taking payment from customers, the page states "Your invoice must include:"

• a unique identification number
• your company name, address and contact information
• the company name and address of the customer you're invoicing
• a clear description of what you're charging for
• the date the goods or service were provided (supply date)
• the date of the invoice
• the amount(s) being charged
• VAT amount if applicable
• the total amount owed

Two of those are routinely missed, and both are dates. The supply date and the invoice date are different fields, and plenty of templates have only one. The supply date is when the work happened; the invoice date is when you billed for it. They are often weeks apart, and which one applies matters for accounting periods.

#The extras for sole traders and companies

GOV.UK adds requirements depending on what you are.

Sole traders — "If you're a sole trader, the invoice must also include:"

your name and any business name being used

an address where any legal documents can be delivered to you if you are using a business name

That second one catches people out. Trading as something other than your own name means you have to give an address where legal documents can reach you. A trading name alone is not enough.

Limited companies — "If your company is a limited company, you must include the full company name as it appears on the certificate of incorporation."

Not the shortened version you use on your website. The name on the certificate.

GOV.UK also notes: "If you decide to put names of your directors on your invoices, you must include the names of all directors." Listing directors is optional — listing some of them is not.

#The unique number is doing real work

A unique identification number is the only item on the list that is purely administrative, and it is the one worth understanding.

It is what everyone refers to the invoice by. Your client's accounts system files it under that number. A payment reference quotes it. When you chase, you say "invoice 0042" rather than describing the work again. Reuse a number across two invoices and you have two documents that cannot be told apart in anyone's records, including your own.

GOV.UK requires it to be unique and says nothing about sequence. Sequential numbering is a convention, not a rule — but it is a convention worth keeping, because gaps in a sequence are visible. If your records run 0039, 0040, 0042, you know to look for 0041. With random numbers, a missing invoice is invisible.

#What is not required, but gets you paid

None of the following appears on the GOV.UK list. All of it changes how quickly money arrives.

A due date, not just an invoice date. "Payable within 14 days" is an instruction someone has to convert into a date. A date is a thing a diary can hold. If your payment terms live only in a contract nobody at accounts payable has read, they are not operative.

Payment details on the invoice itself. Account number and sort code, or the wallet or payment link. Making someone search an old email for your bank details adds a step, and steps are where invoices stall.

A purchase order number, if they use them. In any organisation large enough to have a PO system, an invoice without a PO number is not late — it is unprocessable. It will sit until someone notices and emails you, and that round trip is often two weeks.

The name of the person who approves it. "Attn: " is not decoration. An invoice addressed to a company reaches a general inbox; one addressed to the person who signed off the work reaches someone who recognises it.

A statement of what has already been paid. If a deposit was taken, show it: total, less deposit, balance due. Otherwise someone will query why the number differs from the quote.

#The description line is where disputes start

"Consulting — £2,400" is a clear description to you and an unanswerable question to the person approving it. They were not in the meetings. They are matching your invoice to a budget line and an approval, and they cannot do that from one word.

A description that gets approved does three things: names the work in the words the client uses for it, states the period it covers, and matches the quote or purchase order it came from. "Website redesign — discovery and wireframes, 3–28 September, per quote Q-0117" is one line and it answers every question an approver would otherwise have to ask you.

That is also what protects you in a dispute months later, when neither side remembers what was agreed.

#A note on the app I build

Disclosed interest: Ledgra is mine.

It covers the required fields above — including both dates, which is more than some templates manage — with automatic unique numbering using your own prefix, tax handled inclusive or exclusive at multiple rates, and your logo, signature and payment details carried onto every invoice so you are not retyping them. It does estimates and receipts too, and converts an accepted estimate into an invoice without re-entering the lines.

It also handles the part the GOV.UK list does not cover: who still owes you. Outstanding and overdue on one dashboard, due-date reminders before an invoice goes overdue, and per-client statements. Everything is stored on the phone, and Pro is a one-time purchase rather than a subscription — which felt like the right choice for a tool whose whole job is tracking what you are owed.

The list above is the useful part of this post though, and it applies whatever you invoice with.

#Frequently asked questions