I have an overpayment for 1401 federal since March from last year. Can I claim that on this years return?

I'm not sure.  What was the 1401 overpayment.  Is this a dollar amount for an Estate or Trust tax return?

If this is a 1041 for an Estate or Trust the overpayment would be Refunded or posted to your 2020 (1041) tax return as an estimated payment for 2021.