A deposit labeled Tcs treas 449 tax ref likely relates to a tax refund or adjustment from the IRS or Treasury Department. You should receive a letter or notice in the mail indicating why they made the deposit.
Since the IRS wasn't able to provide you any information, I suggest contacting the Bureau of the Fiscal Service (BFS) at 1-800-304-3107 to check with them about any offsets they may have on record for you.
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