The way property data actually flows in a small letting operation is not tidy. Tenant references sit in one portal, the accounting is in another, maintenance requests come through a third, and the day-to-day chatter - including, quietly, passport photos and bank details - happens in a couple of WhatsApp groups. Each of those made sense when it was added. Together they mean nobody can answer the simple question of where a given tenant's information actually lives.

That fragmentation is the risk. Sensitive documents get shared into a WhatsApp group “just to sort it quickly”, and then they live on several people's phones forever, including the phone of the contractor who left the group months ago. A shared portal login gets passed around and never changed. There is no single place to delete a former tenant's data because there is no single place it was ever kept. The data is not lost - it is scattered, which is harder to fix.

For a tenant, the harm is real. Between a portal, an inbox and a chat group, an operation of this kind holds enough to open credit in someone's name: proof of ID, proof of address, bank details, employment. If any one of those systems or phones is compromised, that is a breach the landlord or agent has to own, and “it was in WhatsApp” is not a defence the ICO finds reassuring.

Pulling this together does not mean buying expensive software. It means deciding on the one place each type of tenant information lives, moving anything sensitive out of chat groups into that place, and keeping a short list of who has access to each system with passwords that are not shared. Then, when a tenancy ends, there is a defined place to go and delete. Knowing where the data is is most of the security.