Yes, there are a number of reasons your refund may not be the amount you thought you were going to get.
First, if you owe the IRS back taxes, they will take it from your refund. If that is the case, the IRS will send you a letter explaining exactly how much they took and where it was applied.
Second, if you owe certain state and federal debts, you may have had a Treasury Offset to pay the debt. Click here to contact Treasury Offset if you think that may be the case.
If you made an easily verifiable mistake on your tax return like entering a figure wrong on your W-2, the IRS may have corrected it before sending you your refund. If that is the case the IRS will send you a letter explaining the change.
If you requested a refund advance, or asked that your fees be paid from your refund, and you owe the bank a debt, they may have taken it from the refund. You can contact TPG customer service, follow this link for more.