A few years ago the UK government found itself in an embarrassing position when it emerged that cabinet ministers had been conducting sensitive official business over consumer WhatsApp. The problem wasn’t just political — it was structural. Personal messaging apps don’t offer the audit trails, data retention controls, or business oversight that handling sensitive information requires.
Your small business probably isn’t making policy decisions over WhatsApp. But you might be sharing client personal data, discussing financial terms, or coordinating on legally privileged matters. The messaging app you use for that matters, and the choice isn’t as simple as “use the secure one”.
What You Actually Need
Before comparing apps, think about what you’re protecting. There are three distinct things people mean by “secure messaging”:
Encryption in transit and at rest. Nobody other than the intended recipients can read your messages. All three of the main options here offer this. End-to-end encryption (E2EE), where only the communicating devices hold the decryption keys, offers the strongest protection. Standard encryption (messages encrypted in transit but the provider can read them on their servers) is weaker but still better than nothing.
Metadata privacy. Who you’re talking to, when, and how often — this is often as revealing as the message content. E2EE protects content but not metadata unless the platform specifically minimises it.
Business administration and compliance. Can your IT admin retrieve messages if an employee leaves? Can you set retention policies? Can you demonstrate to the ICO that you’ve handled personal data appropriately? These are different concerns from encryption, and consumer apps typically fail here.
Signal
Signal has the strongest privacy credentials of any mainstream messaging app. The Signal Protocol (which WhatsApp also uses for its E2EE) was designed by cryptographers and is open source. Signal collects minimal metadata — it can’t tell anyone who you’re messaging or when. Messages can be set to auto-delete. There’s no advertising, no data monetisation.
For a small business, the problems are practical. There’s no admin console. If a team member leaves, there’s no way to retrieve their conversations or revoke access cleanly. There’s no message archiving for compliance purposes. Signal doesn’t integrate with business tools. And critically, you can’t create a proper business presence — it’s a personal phone number, full stop.
Signal is excellent for specific high-sensitivity communications: a solicitor discussing privileged matters with a client, a financial adviser sharing documents that contain personal data, a small business owner talking to their accountant about sensitive financial information. It’s not an all-purpose business communication platform.
WhatsApp Business
WhatsApp Business is designed for, well, businesses. You get a business profile, automated messages, catalogue features, and you can communicate with customers directly. The E2EE protection comes from the same Signal Protocol as standard WhatsApp, so message content is encrypted.
The issues are more subtle. First, Meta’s metadata position: while WhatsApp messages are E2EE, Meta retains metadata — who you communicate with, frequency, device information. Under Meta’s privacy policy, this can be used across its platforms. For businesses handling personal data under UK GDPR, that data transfer to Meta’s infrastructure needs to be accounted for.
Second, business control: WhatsApp Business doesn’t offer proper admin controls for employee accounts. If a member of staff uses their personal WhatsApp Business account for client communications, that data belongs to them personally, not your company. When they leave, so do the conversations.
WhatsApp Business is fine for relatively low-sensitivity customer service interactions — appointment reminders, order confirmations, general queries. It’s less appropriate for anything involving personal data you’d need to retain, audit, or retrieve under a data subject access request.
Microsoft Teams
Teams is the answer if your business is already in the Microsoft 365 ecosystem (most UK businesses using Outlook are). It’s not the most user-friendly messaging app and it’s definitely overkill if you have three employees, but for businesses with regulatory concerns, compliance requirements, or simply a need for proper IT admin, it’s the most capable option.
What Teams gives you that the others don’t:
Admin controls. IT admins can manage who can communicate with whom, what guests can access, and data retention policies. When someone leaves, their account is closed and conversations are retained according to your policy.
Data residency. For UK businesses, Microsoft offers data residency in UK datacentres, which simplifies GDPR compliance arguments about where customer personal data is held.
Audit logs. Every message, file share, and meeting is logged in the Microsoft 365 compliance centre. This is what the ICO means when it asks whether you can demonstrate appropriate handling of personal data.
eDiscovery. If you’re ever involved in a legal dispute where business communications are relevant, Teams messages can be retrieved under legal hold. Consumer messaging apps can’t reliably provide this.
The downsides are real. Teams is complex to administer. The mobile app can be clunky. And if your clients, partners, or suppliers aren’t on Teams, you’re either asking them to create an account (annoying) or using a different channel for external communications anyway.
The Honest Recommendation
For most UK small businesses: use Teams or a similar enterprise platform (Google Chat for Workspace users, Slack with appropriate retention settings) for internal team communications involving anything business-sensitive. Use WhatsApp Business for low-sensitivity customer-facing communications where your customers expect it. Have a policy — even a simple written one — about what goes where.
For businesses in legal services, healthcare, financial services, or anywhere handling sensitive personal data: Signal for specific high-sensitivity communications, Teams for everything else. Consumer WhatsApp should not be the primary channel for business-sensitive conversations.
Document what you’re using and why. The ICO doesn’t require any specific messaging platform. It does require that you’ve thought about data protection and can explain your approach. A short internal policy covering which app gets used for what, with a brief rationale, satisfies that requirement better than most businesses manage.