The amount of rent paid by Council tenants is determined by Cork County Council’s Differential Rent Scheme (pdf). Rents are calculated based on total household income in a manner that ensures that the amount you are charged is reasonable and does not lead to undue financial difficulties. It is a breach of your tenancy not to notify the Council of total household income or of any change of circumstances.
From Spring 2018, all Cork County Council dwellings, including those previously let by the Town Councils, have come under the scope of one uniform Scheme. This has standardised the multiple schemes previously in operation.
Further details on Calculation of Rent (pdf).