Email signature legal requirements: what UK, EU and US rules actually require

“Do I have to put our company number in my signature?” In many countries, yes — or at least in every business email your company sends. The rules differ by country, but they share a logic: business correspondence must identify the legal entity behind it. Here is an overview of the main regimes.

This article is general information, not legal advice. For a specific situation, consult your legal counsel.

United Kingdom

Under the Companies (Trading Disclosures) Regulations 2008, a UK company must show on its business letters, order forms and websites — and business emails are treated as business letters:

• the company’s registered name;
• the part of the UK in which it is registered (e.g. England and Wales);
• its registered number;
• its registered office address.

If the company chooses to mention its share capital, it must be the paid-up share capital. Failing to comply is a criminal offence punishable by a fine. LLPs are subject to equivalent rules.

Germany

German law (the Commercial Code and the laws governing GmbHs and AGs) requires business letters, including emails, to show among other things: the legal form, the registered seat, the register court and registration number, and — for a GmbH — the names of all managing directors (plus the chair of the supervisory board, if there is one). German courts take these obligations seriously.

France

France’s Commercial Code (article R123-237) requires companies to show on all correspondence their SIREN number, the mention “RCS” with the city of the registry, their registered office, and — for commercial companies — their legal form and share capital. Our French version of this article covers the details.

Spain

Spain’s Commercial Registry Regulation requires registered businesses to show their registered address and registration details in their documentation and correspondence. Our Spanish version of this article covers the details.

United States

There is no general federal rule requiring company details in every business email. However, if an email is primarily commercial (promoting a product or service), the CAN-SPAM Act requires, among other things, a valid physical postal address and a working way to opt out. Ordinary one-to-one correspondence with a promotional banner in the signature is generally judged on its primary purpose — worth reviewing with counsel if your banners are aggressive. Regulated industries (financial services, law, healthcare) often have their own disclosure rules.

Regulated professions everywhere

Lawyers, accountants, financial advisers, estate agents and others frequently have extra disclosures set by their regulator: professional title, regulatory body, registration number, professional indemnity insurance. Check your profession’s rules.

What is usually not required

• VAT number: required on invoices, not generally in ordinary correspondence.
• Confidentiality disclaimers: not mandatory, and their legal effect is debated. See our guide to email disclaimers.
• A privacy policy link in every email: not generally required, but useful for transparency — especially if your signature includes measurement. See email signatures and GDPR.

Subsidiaries and groups

Each legal entity has its own disclosures. Someone employed by a subsidiary must show the subsidiary’s details, not the parent’s. It is a strong argument for signatures per entity.

Making sure disclosures never go missing

The problem with legal details isn’t knowing which ones to include — it’s that they disappear from home-made signatures: people find them too long, delete them, or copy a colleague’s signature that never had them.

The fix: put the disclosures in the locked foundation of the template and deploy signatures centrally. They are then present for everyone, always current — and a change of registered office is corrected once.