The Department of Employment Affairs and Social Protection identified welfare overpayments totaling €104m in 2019 through control reviews and recovered €79 million, according to the Comptroller and Auditor General.
609,000 "control reviews" were carried out last year in a bid to detect overpayments and potential fraud - though that was below the target of 757,000 checks, and 43,000 lower than the number of checks carried out in 2018.
However, the overpayments detected varied in scope and value.
When 2% of recipients of Invalidity Pension were checked, 68% of those examined were found to have received overpayments averaging €1,140.
Some overpayments also arose when representatives of deceased claimants delayed in notifying the department.
An audit of 1,165 cases found 441 instances where payments averaging €836 had been made after the claimant's death.
6% of Illness/Disability Pensions were audited, and 11% of those reviewed had received overpayments averaging €415.
37% of Child Benefit Recipients were reviewed, but overpayments were only detected for 1.5% of those audited averaging €19.
Overpayments of €12.2 million arose through "official error" in relation to Illness Benefit, though this was attributed to difficulties in moving to a new system - with issues including an inability to scan certain medical documentation.
Control reviews of various schemes were carried out through mailshots (58%), from a desk without seeking the customer (30%), from a desk while meeting the customer (7%) , through site/home inspections (3%) or through requirements for medical assessments (2%).
The reviews are carried out to establish if there has been suspected fraud, claimant errors or official errors.
The CAG describes the level of "irregular" payments as "material".
He recommends that the Department should address delays in publishing the results of control surveys - which can take up to three years.
The report also urges the Department to ensure it has adequate resources, and to formalise structures for collating and reporting significant control issues.
He also cautions that new systems should be fully tested before being put into operation.
The C&AG also found that the cost of the state contributory pension rose by 40% from just under €4bn in 2013 to over €5.6bn last year.
Government expenditure on social welfare totaled €20.8bn last year - accounting for 24% of general government expenditure, or the equivalent of 6% of GDP.
In 2019, over 1.3 million people were receiving a weekly social welfare payment - with over 630,000 in receipt of monthly child benefit payments.
While total expenditure remained relatively stable, social assistance payments decreased as a percentage of total expenditure - from 57.4% in 2013 to 51.7% in 2019.
However, the cost of "age related social insrurance benefits" including the state contributory pension rose by 40% over the six years from 2013.