It depends. If the taxes have already been withheld, the tax will be credited to your account as a tax payment with the IRS. If the distribution did occur, even though it was not required, you could still receive Form 1099-R and have to report that income.
I suggest consulting your financial planner for information about their particular method of reversing an unneeded RMD.
See this article for information about Reporting Form 1099-R.
Please see these resources for further IRS guidance:
January 27, 2020 IRS Provides relief to financial institutions affected by tax law change raising the age for required minimum distributions
Notice 2020-6 Relief for Reporting Required Minimum Distributions for IRAs for 2020.
IRS Retirement Topics RMDs
