'For you to qualify for rent-a room relief, your home must be located in the State and you must occupy it as your sole residence during the year of assessment. This means that it is your home for the greater part of the year and is where people would normally expect to make contact with you. In most cases, you do not have to own the property – you could be a tenant and be sub-letting to someone else. (In these cases, you should check with your landlord that sub-letting is allowed – see our document on
tenants’ rights and obligations.) However, if you are renting to a HAP tenant you must own the property and provide proof of ownership.'
From this, my understanding is, my son could sublet a room and clain the rent a room relief. This is quite interesting.