If the mother died after her Required Beginning Date for RMDs, the regulations proposed 4 months ago require annual distributions based on the single life expectancy of the beneficiary if the trust is qualified for look-through or based on the life expectancy of the mother if not qualified for look-through. However, it was the belief during most of2021 was that annual RMDs would not be required, so it's not clear why this distribution in 2021 is being referred to as an RMD. Assuming that this part of the proposed regulations becomes final without change, it's unclear what the IRS will say about 2021 RMDs not taken because of the belief that no annual RMDs were required whenever the 10-year rule applied.
When I said that the trustee determines the appropriate amount of the distribution, that assumes that the trustee is basing that determination on the terms of the trust. I didn't mean to imply that the trustee necessarily has discretion in determining the amount. I only meant it to imply that it's the responsibility of the trustee to tell the IRA custodian how much to distribute.
There's a good chance that the trust agreement was written before the SECURE Act was enacted, so the trust agreement might not produce the originally intended result given the changes in the law.
