What to Include on a UK Invoice Legally: A Complete Guide

If you're a self-employed tradesperson or small business owner, knowing what to include on a UK invoice legally is important. Get it wrong, and you risk delayed payments or even issues with HMRC. According to a 2022 survey by the Federation of Small Businesses (FSB), late payments affect 62% of small businesses, many due to incorrect invoicing.

Essential information for every UK invoice

Firstly, every invoice you issue should contain the following core details:

• Your business name and address: If you're a sole trader, you must include your own name as well as the business name.
• The buyer's name and address: Ensure this information is accurate to avoid payment delays.
• Unique invoice number: This must be sequential and help you track payments. It's a legal requirement under HMRC guidelines (GOV.UK).
• Invoice date: The date you issue the invoice.
• Payment due date: Typically 30 days, unless otherwise agreed.
• Clear description of goods or services: Include quantities, unit prices, and total costs.
• Total amount due: This should include any applicable VAT (use our VAT calculator to ensure accuracy).

Additional requirements for VAT registered businesses

If your turnover exceeds the VAT threshold of £90,000, you'll need to register for VAT and include additional information:

• Your VAT registration number.
• Rate of VAT charged per item: Different goods and services can attract different VAT rates.
• Total VAT charged: Separate from the total amount due.

Visit our VAT registration guide for more details on this process.

What makes a good description of services

This is where many tradespeople slip up. Writing "plumbing work — £800" on an invoice is technically not enough. HMRC expects a clear description that links the payment to the work done, and your client needs enough detail to understand what they're paying for.

A good description for a plumber might read: "Supply and fit new combi boiler (Worcester Bosch 30i), including removal and disposal of old boiler, 2 new radiator valves, and system flush. Labour: 2 days." That tells the client exactly what was done and what materials were used.

For electricians, break it down by area or circuit: "Full rewire of ground floor — 8 double sockets, 4 lighting points, new consumer unit (18-way). EICR issued." This level of detail protects you if there's ever a dispute, and it makes the invoice easier to understand for the client.

If you're a builder working on a larger project, itemise by phase or room rather than trying to list every nail and screw. The goal is clarity, not a novel. Use our invoice generator to build professional, detailed invoices without spending ages on formatting.

CIS requirements for construction invoices

If you work in construction as a subcontractor, the Construction Industry Scheme (CIS) adds extra requirements to your invoices. Under CIS, the contractor deducts tax from your payment and sends it to HMRC on your behalf.

Your invoice needs to clearly show:

• Your UTR (Unique Taxpayer Reference) number
• The gross amount for the work
• The CIS deduction rate (20% for registered subcontractors, 30% for unregistered)
• The deduction amount
• The net payment due

For example, a plasterer invoicing £2,000 of labour would show a CIS deduction of £400 (at 20%), with a net payment of £1,600 due from the contractor. The materials portion is not subject to CIS deductions — only labour.

Use our CIS calculator to work out the correct deductions before sending your invoice. Getting this wrong wastes time for both parties and can cause problems with your Self Assessment at year end.

Electronic invoices and Making Tax Digital

With the government's Making Tax Digital initiative, electronic invoices are becoming more common. Platforms like InvoiceAdept's invoice generator can help you comply with these new requirements by creating professional and compliant invoices.

Making Tax Digital for Income Tax Self Assessment (MTD for ITSA) is being rolled out from April 2026 for self-employed individuals and landlords with income over £50,000. This means you'll need to keep digital records and submit quarterly updates to HMRC. Having a digital invoicing system in place now means you're already ahead of the game.

Legal considerations for late payment

Under the Late Payment of Commercial Debts Act 1998, businesses can charge interest on overdue invoices. The statutory interest rate is 8% plus the Bank of England base rate. Use our late payment interest calculator to determine the interest you can charge.

Including a clear statement on your invoice about late payment charges is both a deterrent and a protection. Something like: "Interest will be charged on overdue invoices at 8% above the Bank of England base rate, in accordance with the Late Payment of Commercial Debts Act 1998." You don't need to charge it every time, but having it on the invoice means you can if needed.

Common mistakes and how to avoid them

Many small businesses suffer from late payments due to simple invoicing errors. Here's what to avoid:

• Inaccurate information: Double-check all details to ensure accuracy. A wrong address or misspelled company name can give a client an excuse to delay payment while they "query" the invoice.
• Lack of detail in item descriptions: Be as descriptive as possible to avoid disputes. Vague line items invite questions.
• Omitting payment terms: Clearly state terms to avoid ambiguity. Without written terms, the default under UK law is 30 days, but you can't enforce shorter terms if they're not on the invoice.
• Missing bank details: It sounds obvious, but forgetting to include your sort code and account number (or payment link) is one of the most common reasons invoices sit unpaid. Make it as easy as possible for the client to pay you.
• Not numbering invoices sequentially: HMRC requires sequential numbering. Gaps or duplicates in your invoice numbers can raise red flags during an inspection.

For builders, specific tips are available in our invoicing guide.

How long to keep your invoices

Once you've issued an invoice, you need to keep a copy. HMRC requires sole traders to keep records for at least five years after the 31 January submission deadline of the relevant tax year. Limited companies must keep records for six years from the end of the financial year.

Digital storage is perfectly acceptable and much easier to manage. If you're using InvoiceAdept, your invoices are stored automatically. If you're using templates in Word or Excel, set up a folder structure by tax year and back up to cloud storage. Losing your records can result in penalties of up to £3,000 from HMRC, so it's worth getting organised now.

For a more detailed breakdown, see our guide on how long to keep invoices for HMRC. And if you need to calculate your day rate to make sure your pricing is right, our day rate calculator is a good starting point.

FAQs

1. What happens if I don't include all required information?

   Your client may refuse payment or delay it until a corrected invoice is provided. HMRC may also question incomplete invoices during an inspection, particularly if VAT is involved.

2. Do electronic invoices need signatures?

   No, electronic invoices don't require signatures to be valid according to UK law. They just need to contain all the required information and be agreed upon as a format by both parties.

3. Can I send an invoice via email?

   Yes, emailing invoices is legally compliant and often preferred for speed and efficiency. PDF attachments are the most common format.

4. How soon should I send an invoice after completing a job?

   Send invoices as soon as possible, ideally on the day you complete the work. Every day you delay sending the invoice is another day added to your payment wait.

5. What should I do if a client disputes an invoice?

   Contact the client promptly to discuss and resolve any discrepancies. If the dispute is about the amount, refer back to the original quote or written agreement. Keep all communication in writing for your records.

Invoice templates vs building invoices from scratch

Some tradespeople still create invoices from scratch every time — typing out their details in Word, manually calculating totals, and saving as a PDF. It works, but it's slow and error-prone. One typo in your bank details and the payment goes to the wrong account (or the client uses it as an excuse not to pay).

A template saves you from re-entering the same information every time. Your business name, address, bank details, VAT number, and standard payment terms are pre-filled. You just add the client details, describe the work, and enter the amounts.

Better still, use an invoicing tool like our invoice generator that handles the formatting, numbering, and calculations for you. It produces clean, professional PDFs that look good and contain everything HMRC requires. No fiddling with margins, no forgetting to update the invoice number, no sending an invoice with last month's date on it.

For tradespeople who do a mix of small and large jobs, having a consistent invoice format builds trust with clients. A professional-looking invoice signals that you run a proper business, which makes clients more confident about paying you promptly and hiring you again.

Your bank details and payment instructions

This might seem obvious, but you'd be surprised how many invoices go out without clear payment instructions. Your invoice should include:

• Account name: The name on your bank account (this must match your business name or trading name).
• Sort code and account number: Double-check these. One wrong digit means the payment goes nowhere.
• Payment reference: Tell the client what reference to use (usually the invoice number). This makes it much easier to match payments to invoices when you're checking your bank statements.

If you accept other payment methods — PayPal, card payments, or online payment links — include those too. The more options you give, the fewer excuses a client has for not paying. Some invoicing tools let you include a direct payment link on the invoice so the client can pay with one click.

If you're working out what to charge in the first place, our day rate calculator helps you set a rate that covers your costs and delivers a fair income.