If you rent out a room (or rooms) in your home to private tenants, any rental income you earn will be exempt from income tax, PRSI and Universal Social Charge, provided this income does not exceed €14,000 in the tax year. This is called the rent-a-room relief.
The relief applies only to residential tenancies, not to short-term guest arrangements. Your tenants must be using the room on a long-term basis. For example, renting a room to a student for the academic year is covered, but taking in guests for short breaks is not.