The Public Accounts Committee is raising questions around the failure to collect €5.3m in motorway tolls last year.
eFlow - which runs the barrier-free M50 toll - wrote off the charges last year.
The company says the fees are "uncollectable".
The revelation is contained in Transport Infrastructure Ireland's financial statements for 2016.
PAC chair Sean Fleming thinks the toll operator needs to improve its collection system.
"There has to be some systematic way to of collecting some of these tolls," he said.
"I'm sure there's some repeat offenders in there from Ireland, and I think people will want to know what measures they're putting in place to make sure that people who use the toll roads pay like everybody else has to do."