Can I return 2020 RMD funds that have been received this year, to reduce my taxable income?

[Bsch4477]

August 31 was the deadline to return that distribution. 

[dmertz]

Assuming that the distribution does not qualify as a coronavirus-related distribution, if the distribution was made within the last 60 days you still have time to roll it over before the regular 60-day rollover deadline.  However, if the distribution was from an IRA, the distribution is still subject to the one-rollover-per-12-months limitation.  Only distributions made before July 2, 2020 had the rollover deadline extended to August 31, 2020.