The British government has launched an investigation of Serco Group, parent company of the firm recently awarded $1.2 billion to manage key elements of the U.S. health-care law’s rollout.

That contract, announced in late June, is among the largest Affordable Care Act grants made so far, expected to cover the hiring of 1,500 workers who will process a wave of health coverage applications.

In the United Kingdom, Serco Group reportedly overbilled the government by “tens of millions of pounds” under a contract to monitor offenders on parole and individuals released on bail, according to an audit conducted by the country’s Justice Ministry.