You may not always get all the tax refund you calculated on your tax return. There are several reasons your refund check might be smaller or possibly larger than you expect.
First, the obvious: If the IRS finds a math error or other mistake on your return it will correct the amount of your refund. The IRS also will deduct certain past due amounts you may owe, such as federal and state taxes, student loan payments or child support, and apply your refund to what is owed. If these adjustments are made, the IRS will send you a letter of explanation. You'll also receive a letter from the Department of Treasury's Financial Management Service indicating where your refund money is being redirected [source: IRS].