It appears that the 2021 Form 8915-F won't be available in Turbotax until March 24, so I will hold off on filing for 2021 until after that date. I did file an amended 2020 return, eliminating one-third of the distribution amount from my gross income and reducing my 2020 tax liability. The IRS indicated that it may take 16 weeks to receive the resulting refund for 2020.
