Around 5000 calls per day are being made to a special Revenue Commissioners phoneline dealing with property tax queries.
960,000 letters were issued to householders in the past week outlining their obligations for 2014.
Although extra staff have been deployed to answer calls, Revenue says wait times for the helpline are around 15 minutes. That rises to 17 minutes if the query needs to be transferred to a Revenue official.
Ministers have today been briefed on the latest controversy surrounding payment methods for the Local Property Tax.
Revenue Chairman Josephine Feehily is also due to answer questions at the Oireachtas finance committee on Thursday.