Furnishing alone does not usually give a landlord a separate right to increase the rent or bypass rent-increase rules. The permitted increase depends on the tenancy, its location, applicable rent-control rules, and the required notice and review limits; furnishings may be relevant when assessing the property’s market rent. Ask the landlord for the calculation and check the latest RTB guidance and rules on gov.ie. If you believe the increase is invalid, the RTB dispute resolution process or a solicitor can assess the individual facts.