The first batch of warning letters to owner-occupiers, believed not to have paid the charge, was issued last week. Up to then only landlords or second home owners had been sent letters reminding them of their household charge liabilities.
However, even homeowners who paid the charge before the payment deadline of March 31st are receiving the new letters.
A spokeswoman for the agency said the letters were being issued to people who had paid because of “imperfections” in the data set being used to identify non-payers.
The second home owners who had not paid the charge were identified using the non principal private residence register (NPPR) database and the register of private rented accommodation held by the Private Residential Tenancies Board.
The new letters, sent to single-home owners, use information from the Property Registration Authority.