PRTB sending out letters to non registered landlords

[Bronte]

Are the PRTB actually sending out letters to non registered landlords and how do they know who they are?

Also are the revenue liasing with the PRTB? In the sense of looking at landlords tax returns and checking that they are registered with the PRTB.

 

[ClubMan]

Also are the revenue liasing with the PRTB? In the sense of looking at landlords tax returns and checking that they are registered with the PRTB.

I thought so ever since PRTB registration became a sine qua non for the landlord to be able to set mortgage interest against rental income when making a tax return?