The Internal Revenue Service said that bankrupt Overseas Shipholding Group Inc., the largest U.S. tanker operator, owes $463 million in U.S. taxes and interest, Bloomberg News reported yesterday. The company owes $27.9 million in interest on $435.1 million of taxes, the IRS said in papers filed on Monday with Kurtzman Carson Consultants LLC, the agent processing claims for Overseas. The IRS labeled it an unsecured priority claim, meaning that the agency wants it paid ahead of other unsecured and lower-ranking debts. Overseas, based in New York, filed for bankruptcy last year after global shipping rates fell and the company gave up trying to win a federal loan guarantee. Overseas listed assets of $4.15 billion and debt of $2.67 billion in its chapter 11 petition.