Almost €560m was paid last year in unpublished tax settlements to Revenue with the top 20 cases yielding more than a third of the total.
Revenue said there had been 62,810 cases settled last year with the average back-payment working out at around €9,000.
The top 20 cases however, accounted for €205m in payments to Revenue, around €10.3m for each of them.
Figures show that the finance and insurance industry was the largest offender with just over €85m worth of "unpublished compliance interventions".
It was followed by the motor industry at €62.8m and the area of public administration and defence where €53.5m worth of settlements were made.
Other sizable payments included €43m from businesses in the arts, entertainment, and recreation sector and €48m from manufacturers of computers and other electronic products.
There was €38m in settlements from the transport and storage sector, €32m from the real estate business, €27m from "IT and other information services", and €22.9m paid out by the construction sector.
The Revenue Commissioners said just over 70% of the settlements - worth €397m in total - were made by almost 39,000 companies.
There was a further €153m of back-paid tax from 21,685 individuals, according to records covering 2024.
Around €1.5m was paid by partnerships, €721,000 by trusts, and €7m by unincorporated bodies.
A spokeswoman said Revenue's mission was to collect taxes in a fair and efficient way which included supporting voluntary compliance.
"Where appropriate, a risk intervention may be conducted to confront cases displaying non-compliance indicators and/or challenge aggressive tax planning," she said.
The spokeswoman said Revenue used a three-phase compliance framework which offered people the chance to correct errors or make disclosures of unpaid tax.
"Taxpayers who avail of opportunities to review their tax compliance position and voluntarily address or disclose any issues identified may benefit by experiencing the minimum level of penalty and generally not risk either publication or prosecution," she said.
Reporting by Ken Foxe
