Billdrop
Log inSign up

UK Invoice Requirements: What HMRC Requires

Whether you're a freelancer, contractor, or small business owner, understanding HMRC's invoice requirements is essential for staying compliant and getting paid on time. This guide covers everything you need to include on a UK invoice — and you can create a compliant UK invoice for free with Billdrop.

Mandatory Fields on Every UK Invoice

HMRC requires all UK businesses to include the following information on every invoice they issue. Missing any of these can cause payment delays or compliance issues.

  1. 1

    Unique invoice number

    Every invoice must have a unique sequential reference number so you and your client can track it easily.

  2. 2

    Your business name and address

    Include your full trading name and business address. Sole traders may use their personal name and home address.

  3. 3

    Client's name and address

    The full name (or company name) and address of the customer you are invoicing.

  4. 4

    Invoice date

    The date the invoice is issued. This is used to determine payment terms and tax periods.

  5. 5

    Description of goods or services

    A clear description of what you supplied — vague descriptions like 'services rendered' may not be accepted.

  6. 6

    Amount charged (excluding VAT if applicable)

    The net price for each line item. If you are not VAT registered, this is simply the price agreed.

  7. 7

    Total amount due

    The grand total your client owes, including any VAT if you are registered.

Billdrop's free invoice creator automatically includes all these mandatory fields so you never miss one.

VAT Invoice Requirements

If your business is VAT registered (i.e. your turnover exceeds £90,000 or you have voluntarily registered), you must issue a VAT invoice and include additional fields on top of the standard requirements.

Additional fields required for VAT-registered businesses:

  1. 1
    Your VAT registration number — Your 9-digit UK VAT number, usually displayed as GB 123 4567 89.
  2. 2
    VAT rate applied — The rate of VAT charged (e.g. 20% standard rate, 5% reduced rate, or 0% zero rate).
  3. 3
    VAT amount charged — The actual pound amount of VAT being charged on each line or in total.
  4. 4
    Total including VAT — The final total your client must pay, with VAT included.

Note: If you are not VAT registered, you must not charge VAT or display a VAT number on your invoices.

Invoice Numbering Rules

HMRC requires that invoice numbers are:

  • Sequential — each new invoice must have a higher number than the last
  • Unique — no two invoices can share the same number
  • Unbroken — gaps in your sequence may raise questions during an HMRC audit

You can choose any format you like — for example INV-001, 2024-0001, or ACME-001— as long as it's sequential and unique. Billdrop automatically assigns sequential invoice numbers when you create an invoice.

How Long to Keep Invoices

HMRC has specific record-keeping requirements depending on your tax status:

VAT Registered

6 years

You must keep VAT records, including all sales and purchase invoices, for at least 6 years.

Self Assessment

5 years

Self-employed individuals and sole traders must keep records for 5 years after the relevant tax year.

Tip: Store digital copies of your invoices to make record-keeping easier. HMRC accepts digital records.

Common Invoice Mistakes to Avoid

These are the most frequent errors UK freelancers and small businesses make on their invoices:

✗ Missing or duplicate invoice numbers

✓ Always use a unique, sequential number. Don't reuse numbers even for amended invoices — issue a credit note instead.

✗ No VAT number (if VAT registered)

✓ If you are VAT registered, you must display your VAT registration number on every invoice. Omitting it means your client can't reclaim VAT.

✗ Wrong or missing invoice date

✓ Use the date the invoice is issued, not the date work was completed. The invoice date affects payment terms and VAT returns.

✗ Vague service descriptions

✓ Be specific about what you provided — include dates, project names, or quantities where relevant.

✗ Incorrect VAT calculations

✓ Double-check your VAT amounts. At 20%, the VAT on £1,000 is £200, making the total £1,200. Simple errors can cause issues with HMRC.

Create HMRC-Compliant Invoices Free

Billdrop automatically includes all mandatory HMRC fields, supports VAT, and generates sequential invoice numbers — so you can focus on your work, not paperwork.

Create Your First Invoice — It's Free

No sign-up required. Download as PDF instantly.