Posted on 23 July 2026

UK Email Signature Legal Requirements (Companies Act Explained)

Most people don’t realise that in the UK, a business email is treated in law much like a letterhead. If you run a limited company, that means your emails — and therefore your signature — must carry certain details by law. Here’s what’s required and why it matters.

This is general guidance, not legal advice. If in doubt, check with your accountant or solicitor.

What the law says

Under the Companies Act 2006 and related regulations, UK limited companies (and LLPs) must disclose certain information on their business letters, order forms and websites — and this has long been interpreted to include business email. The required details are:

• The company’s registered name (e.g. “Example Trading Ltd”).
• The company registration number.
• The place of registration (e.g. “Registered in England and Wales”).
• The registered office address.

If your company is VAT-registered, it’s also good practice to show your VAT number where relevant.

Who this applies to

This applies to limited companies and LLPs. Sole traders and ordinary partnerships aren’t bound by the same disclosure rules, though showing clear contact details is still sensible.

How to add it without cluttering your signature

The legal details don’t need to dominate. Set them in a smaller, muted font as a final line or two beneath your main signature block — present and readable, but visually secondary. A single line such as “Example Trading Ltd, registered in England and Wales no. 12345678. Registered office: 1 High Street, London, EC1A 1AA” does the job.

Keeping it consistent across the team

The risk with legal details is inconsistency — one person updates the office address, forty others don’t. A managed signature keeps the compliant wording identical across everyone automatically. Mirosign lets you standardise the whole team without per-user fees.

See how it fits into a clean layout in our complete setup guide, then build a compliant signature free →