The body, which runs Leinster House, was forced to pay €333,412 to the Revenue Commissioners. The amount included more than €100,000 in interest and penalties.
The exposure arose from its failure to properly account for certain taxi services for staff travelling home, meal allowances and other employee perks.
Late last year, Revenue originally hit the Oireachtas with double the amount of penalties after it decided the commission had deliberately avoided its taxes.
However, this was lowered to a lesser sanction following negotiations which branded its actions careless.
In the last two years, other public bodies — Fás, Cork County Council, Kerry County Council, and County Cork VEC — have made settlements with the Revenue for failing to fully declare their taxes.
However, these bodies avoided being listed among the defaulters because they made a full voluntary disclosure.
In a statement, the Houses of the Oireachtas said it had approached Revenue voluntarily in December 2012 and this triggered a full audit.
It said it has revised its taxi policy.
“The Houses of the Oireachtas Service has had an ongoing practice to provide taxis to staff who stay late to perform official functions for the Houses of the Oireachtas.
“During analysis of all trips taken during the course of the last three years, it was apparent that many taxis taken from work to home were taken outside of Revenue allowable taxi journeys,” it said.
Apart from the Houses of the Oireachtas, the largest amount to appear on the latest Revenue defaulters list was a €2.6m bill landed on retired medical consultant Maurice Fenton, of Knocklion, Cunningham Road, Dalkey.
This included a €1.3m penalty for under-declaring income tax and capital gains taxes.
Another medical consultant, Paul Byrne, at Kyneglass House, North Circular Rd, Limerick, had to pay €345,000 following an audit.
A casino operator, Harlechdale Ltd, is currently in liquidation but was still left with a bill for €978,775.
The company operated from a premises on St Patrick’s Quay, Cork.