If when you filed your return you selected to the option to Pay With My Refund, this option allows you to pay your TuboTax fees from your refund instead of paying them out of pocket. TurboTax works with a third party bank to process this for you and they also charge a processing fee. You should have received information from TurboTax explaining the details of the transaction and the costs involved with it. These fees would not be the $750 that you mentioned, were taken from your refund.
Another thing that may have happened is that the IRS may use some of your refund to pay off past-due federal debt. You should first contact the agency to which you owe the money to find out if your debt was submitted for a tax refund offset. Usually the Department of Treasury's Bureau of the Fiscal Service (BFS) issues a letter if an offset occurs. This is the agency that issues IRS tax refunds and Congress authorizes BFS to conduct the Treasury Offset Program (TOP). If you don't receive a notice, you can contact them at 800-304-3107 (or TTY/TDD 800-877-8339).
The IRS also issues notices if they make changes to your refund, and also post updates of any changes on Where's My Refund?.
@LisaAndrew
