The new tax bill eliminated the RMD I owed for 2020 filing. What happens to the federal tax that was withheld by the custodian when the RMD was issued to me?

[RChisholm]

Yes, I reported it all, it says "rollover" on line 4 b, and the federal tax tax withheld was included on line 25b.   But I included the entire amount when I rolled it all back over into my IRA, including the federal tax amount withheld.   Doesn't that mean I paid the federal tax twice?    The federal tax was $1200 which was withheld and included in my overall tax obligation, and then another $1200 I paid with private funds back into the IRA.     I think I would be fine had I rolled over the entire amount LESS the $1200 federal tax.   

[dmertz]

You didn't pay any tax on the distribution.  What was withheld was either refunded to you by the IRS or reduced the balance that would otherwise have been due with your 2020 tax return.  The refund or reduction in balance due replaced the funds that you substituted to complete the rollover.