Up to 40 local authority tenants will have a 100-euro-a-week penalty added onto their rent from early next month.
The results of a recent rent review will come into effect from the 4th of April.
Two thirds of tenants will see their rent fall, stay the same or rise by a very small amount.
But up to 40% will see a significant increase.
Mary Mulholland, from Kilkenny County Council, says the €100 penalty will only affect tenants who’ve refused to update their household incomes with the local authority.