When the rent is late, the tenant should be contacted immediately. This lets the tenant know you are a professional landlord and on top of things.
A gentle reminder is usually enough to prompt tenants to pay their outstanding rent. If the rent remains outstanding the landlord must notify the tenant in writing that the rent is owing and give them 14 days to pay the rent.
If the rent continues to be outstanding the landlord may serve a Notice of Termination on the tenant. The notice must comply with the Residential Tenancies Act 2004 in terms of the content of the notice itself and the amount of notice given.