If I understand correctly, it's your tenant who has sent you the form not the DHSS. I am in receipt of Pension Credit and therefore receive Housing Benefit. My benefit has nothing whatsoever to do with my landlord. It's me who claims and me who receives the benefit. I then pay my landlord monthly directly to her bank account. In order to claim I have to complete the lengthy form, which includes the name and address of my landlord and provide a copy of my tenancy contract.
I can only suggest that maybe your tenant is paying cash with a rent book and possibly there's a section in the form which you need to complete to confirm the tenant's rent, etc. Why not call the council? They are usually very helpful and won't be intrusive about your situation - they only want to know about the tenant's situation. And no, there's no way they would have any control over your property!
Maybe your tenant