Seven Revenue and Customs staff have been sacked for deliberately under-paying benefits to ethnic minorities.
It follows an internal investigation into nine men based at the HM Revenue and Customs call centre in Belfast.
Two resigned after it began and seven were dismissed on Tuesday.
They are believed to have tampered with computer records to ensure ethnic minorities living across the UK did not receive the benefits they were entitled to. All have now been fully reimbursed.
It is understood about 200 people work at the contact centre.
The allegations of racially-motivated gross misconduct were investigated last January when a complaint was lodged by somebody who said that their records had been changed.
A detailed audit was carried out and the inquiry then widened it to take in another 16 child benefit cases.
It is understood the nine men were suspended once the investigation started, but two quit immediately.
Dave Hartnett, permanent secretary for tax at HMRC, said the department operates a zero-tolerance policy on racial discrimination.
"The vast majority of our people are entirely professional and one of the ways we support that professionalism is by taking decisive action against the tiny minority who let us all down by falling far short of those standards," he said.
Later on Wednesday, a Public and Commercial Services Union spokesperson said: "PCS campaigns hard against any form of racism or discriminatory behaviour.
"We have concerns about procedural issues and will be seeking to raise these with the employer."
The HMRC contact centre is based at Dorchester House, close to the city centre in Belfast's Great Victoria Street.