Do I have to register with the PRTB?

Well, not me, but a friend of mine lives (PPR) outside Dublin but has a 3-bed apartment in Dublin which he stays in when he's in the capital. He rents two rooms (to licensees). He pays tax as required.

1. Is he required to register with the PRTB? They seem to be non-committal on the matter.
2. If not required to register with the PRTB is he still entitled to account for mortgage interest paid when calculating tax owed?

If he has a written lease agreement, he may have difficulty in proving they are licensees. Furthermore, if they have lease agreements, then he is not permitted to enter the property without the tenants' express permission.

If he has a written Licensee agreement or no verbal tenancy agreement then he he is a live-in landlord with unrestricted access to the property and does not have to register with the PRTB.

As regards the mortgage interest I will have to leave that to someone more familiar with the tax system but I believe he cannot claim the interest paid.