The Department of Treasury's Bureau of the Fiscal Service (BFS) issues IRS tax refunds and Congress authorizes BFS to conduct the Treasury Offset Program (TOP). Through the TOP program, BFS may reduce your refund (overpayment) and offset it to pay:
For further assistance, contact the BFS's TOP call center at 800-304-3107 to find out if your refund was reduced due to an offset.
You may want to request a "Record of Account Transcript" from IRS to see what happened. The IRS may have changed an amount on your return during processing, but for some reason you didn’t receive a notice.
Record of Account Transcript - combines the tax return and tax account transcripts into one complete transcript. This transcript is available for the current tax year and returns processed during the prior three years using Get Transcript Online or Form 4506-T at: https://www.irs.gov/individuals/get-transcript