If you are receiving less than you should, you may have an offset on your Federal or State refunds.
The Bureau of the Fiscal Service (BFS) issues Federal tax refunds. They are also authorized by Congress to reduce your refund if you owe any debts.
You'll get an explanatory letter from the BFS if your refund is offset for any of these debts. The remainder of your refund will be processed as usual; an offset shouldn't delay it, unless of course your entire refund was applied to your debt.
To determine whether an offset has occurred on a debt owed, contact BFS's TOP call center at 800-304-3107 or TDD 866-297-0517, Monday through Friday 7:30 a.m. to 5 p.m. CST.
More info about refund offsets, including contact info and the appeals process, is on IRS.gov (Tax Topic 203).
To find out about a debt that reduced your state refund (if applicable), you will need to contact your State Department of Revenue.