Tens of thousands of people may have been given the wrong disability benefits over several years, the state benefits agency UWV has confirmed.

The mistakes relate to WIA benefits, paid to people who have been ill for more than two years and are unable to work or to carry a full-time job.

The agency is currently trying to establish how many people have been affected and expects to complete the probe in December. It will then get in touch with those who have been affected.

UWV chief Joanna Hirscher told broadcaster NOS that the agency had been under pressure for years. “We get more claims every year,” she said. “We have not paid enough attention to the quality of our calculations.”

Social affairs minister Eddy van Hijum said that he is shocked by the high number of errors. “We cannot rule out tens of thousands of benefits being wrong,” he told MPs.

The minister said officials are also looking to establish who may have to pay back some of the money. Some of the errors may already have been corrected because the claimants themselves raised issues, he said.

The UWV said that in principle people who are paid too much in error do not have to repay the cash. But people who should have known the amount was wrong will be carefully checked, a spokesman said.

WIA benefits are based on 70% of last earned salary up to a maximum of € 282.95 a day, but are subject to a complex calculation based on how fit the claimant is.

Some 850,000 people in the Netherlands are claiming some sort of incapacity benefit and the majority are receiving WIA.