Investigations by the Criminal Assets Bureau in 2011 led to almost €6 million being returned to the Exchequer.
According to the latest CAB annual report, the bureau collected €2.7m from the proceeds of crime and €3.8m from uncollected taxes and interest.
A further €454,000 was collected in overpaid social welfare benefits in 2011.
The Criminal Assets Bureau said it also saw an increase in the number of fraud cases that year.
In one case, it managed to recover over €2.6m from criminal activity, which it passed to a liquidator to be shared amongst the victims of that particular fraud.
In addition to the €3.8m CAB collected on behalf of the Revenue Commissioners, it also seized a Range Rover Discovery worth over €82,000, which it gave to the State.
CAB investigations also revealed social welfare overpayments of €1.5m. By the end of 2011, €454,000 of this had been recovered.
Actions were taken against 120 people who were illegally claiming social welfare benefits and these payments were either reduced or cancelled, which resulted in a saving to the State of €616,500.