Landlords should keep the tenancy agreement, records of rent paid, rent receipts or bank statements, and copies of any rent-increase notices. They should also retain the calculations and supporting information used to justify the new rent, including the previous rent and the date it was last set where relevant. These records can be important if the increase is challenged through the Residential Tenancies Board (RTB). The RTB or a solicitor can advise on what evidence is required in the circumstances of a particular tenancy.