Uber Technologies (UBER) shares reversed earlier gains in premarket trading Tuesday after the ride-sharing group said its tax affairs are being examined by the U.S. Internal Revenue Service.

In its 10-Q filing to the Securities and Exchange Commission for the quarter ending on March 31, Uber said the IRS will look into its federal tax filings for the years 2013 and 2014, and added that state and international revenue authorities were also examining its previous filings. 

"Although the timing of the resolution and/or closure of audits is highly uncertain, it is reasonably possible that the balance of gross unrecognized tax benefits could significantly change in the next 12 months," Uber said. "Given the number of years remaining subject to examination and the number of matters being examined, the Company is unable to estimate the full range of possible adjustments to the balance of gross unrecognized tax benefits."

"The Company does expect the gross amount of unrecognized tax benefits to be reduced within the next twelve months by at least $141 million, which is related to ongoing matters with tax authorities regarding the Company's transfer pricing positions," Uber added.

Uber shares were marked 0.17% lower in the opening hour of trading following the SEC filing, after earlier rising nearly 2.6%, change hands at $41.15 each, a move that would leave the stock 85 cents south of it opening trade when the stock listed on the NYSE on May 10.