I might be missing something, but if dad died after his RBD and was recalculating his life expectancy, that life expectancy drops to zero in the year following his death, but if the Trust qualified as a Designated Beneficiary Trust, then dad was entitled to use the JOINT life expectancy of himself plus the beneficiary with the shortest life expectancy, modified by the MDIB rule (making the daughter 10 years younger than dad for RMD purposes).
It appears to me (again, I might be missing something) that the remaining distribution period is now the oldest daughter's life expectancy, per table V (NOT modified by MDIB) in the year of Dad's first required distribution, less the number of years elapsed since.
The entire IRA would, indeed, be required to be distributed by 12/31 of the year following Dad's death IF THE TRUST DID NOT QUALIFY AS A DESIGNATED BENEFICIARY TRUST (e.g.: all beneficiaries were not identifiable, not individuals, etc.)
If I'm wrong (which is ALWAYS possible), I shall appreciate correction.
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John L. Olsen, CLU, ChFC
Olsen Financial Group
St. Louis, MO