If you owe delinquent state income taxes, back child support, or delinquent non-tax federal debs such as student loans, etc., the Department of Treasury's Financial Management Service (FMS), which disburses IRS refunds, may offset your refund for the delinquent amount.

FMS will deduct the past-due amounts from the payment that appears first on the payment file received from IRS (the IRS payment file orders accounts from the lowest to the highest routing number). If the debt exceeds the payment designated for the account that appears first on the payment file, FMS will reduce the payment designated for the account that appears next, etc.

You will receive a letter from FMS explaining any offset amount, the agency receiving the payment, the address and telephone number of the agency, and amount of your refund/direct deposit offset. If you dispute the debt, you should contact the agency shown on the notice, not IRS, since IRS has no information about the validity of the debt.

Information about refund offsets is available through Where's My Refund?

Source: www.irs.gov