A report released Tuesday by the inspector general for the Commerce Department reveals that Vikrum Aiyer, the former chief of staff for the U.S. Patent and Trademark Office during the Obama administration, was charging taxpayers for his taxi rides to and from work, to the tune of about $4,000.

In Aiyer’s role under Obama, he was responsible for managing a $3.4 billion budget and supporting 13,000 employees at the Patent and Trademark Office, according to a report in The Washington Free Beacon.

The Washington Post reported that Aiyer was usually picked up on a street corner a tenth of a mile from his home in Washington, D.C., according to the report. But he wrote on the invoice that he was leaving from Commerce Department headquarters in downtown Washington.

He once billed the government for a $54 taxi ride from his home to the Alexandria office on a Saturday, then $36.20 for a return trip that evening after a party, investigators found, concluding that he “used the Agency’s Cab Company account to facilitate his weekend social activity in this particular instance, but he made it appear otherwise when arranging for these cabs.”

Aiyer also racked up $15,000 in expenses on his government-issued credit card, charging for food and drink at local bars, clubs, coffee shops, restaurants, grocery stores, dry cleaners and at least one liquor store, the report said. Investigators said he personally paid off the expenses.

Aiyer commuted across the Potomac River 10 miles or so to work on at least 130 occasions over the course of two years, the majority during a four-month stretch in 2016.

To escape detection, Aiyer impersonated current and former high-level agency officials, writing their names on cab receipts and vouchers he submitted to the taxi company, which then billed the government, investigators found.

One of those officials was the Patent and Trademark Office’s then-communications director, whose supervisors eventually confronted him on his apparent taxi usage. In response, he noted that he regularly drove to work and his car was in the agency’s parking garage.

Prior to resigning with thousands of other Obama political appointees before Donald Trump took office last year, Aiyer was interviewed by investigators in December 2016 about the taxi rides. He did not deny their findings, according to the report.

The former official’s unauthorized taxi rides went unnoticed for at least two years by budget officials who looked over Alexandria Yellow Cab invoices. The patent office paid the company more than $4,000 for Aiyer’s rides, according to the report.

When initially confronted about billing the taxi rides to the government, Aiyer told investigators that it was standard practice for officials at his level in the agency, naming several officials who told him that they did the same thing.

“Political Appointee said he thought it was permissible to provide incorrect trip origin or destination information because this was the ‘protocol that was imparted to [him] by [his] bosses at the time,’ and ‘because this is how . . . prior bosses approach[ed] it,’” investigators wrote.

Aiyer currently serves as the vice president for public policy and strategic communications at a San Francisco company.