Yes I have had a few such cases with clients. Unfortunately as you know interest is not an allowable deduction unless, for the relevant tax year, ALL tenancies in the relevant property were registered with PRTB. I have had instances where clients might have had at the start of the year an ongoing tenancy coming into that year, then the tenant leaves and the next tenant, for whatever reason didn't get registered then maybe that tenant was gone by end of year and another tenant comes in and is registered. The middle tenancy not being registered cuts off interest for the WHOLE year. People find that very unfair. Revenue recently issued a bulletin that once the tenancy was registered by the return filing deadline for the relevant year then it was considered to be ok. Unfortunately once the tenancy has ended the PRTB are not allowing late registrations. The late registration must be for a tenancy still in operation. It is a problem but I don't see a solution as Revenue are very clear on the matter.