I received a different amount on my federal return than expected. How do I find out what happened. It’s thousands less than expected.

[rangerrick1969]

I was supposed to receive 3814.00 on my federal return. That includes the stimulus that turbo tax said I qualified for being that I only received one stimulus check. My return this morning was 598.00

[MinhT1]

Your refund may have been changed by the IRS for reasons that are unknown to us. You will soon receive a notice from the IRS explaining the changes.

Another reason could be that your refund may have been partially offset by the IRS for some debts, such as past due taxes, cild support,...

Please read this IRS document, especially the paragraph Why is my refund different than the amount on the tax return I filed? 

[SweetieJean]

Was the $598 a State refund maybe?  It comes separately from Federal.