There is no "partial year" when determining RMDs; RMDs are calculated as a yearly amount. However, any part of year-of-death RMD required to be taken by the deceased that was not satisfied by the deceased prior to death is the combined responsibility of the beneficiaries. The beneficiaries can satisfy the remainder of the deceased's year-of-death with any combination of distributions paid to the beneficiaries.
Provided that a separate account for each designated beneficiary was established by December 31, of the year following the year of death, each beneficiary will be required to calculate and take their own RMD as beneficiary from their own inherited IRA account. If separate accounts were not established, RMDs are based on the age of the oldest designated beneficiary.
See IRS Pub 590-B regarding the determination of the amount of RMDs:
https://www.irs.gov/publications/p590b/ch01.html#en_US_2016_publink1000230753
Here are more specifics: The deceased died in May, 2016 at age 92. There were multiple beneficiaries, allocated equally. Prior to death the RMD was being paid monthly from the deceased's IRA, so it was partially paid at the time of death. One beneficiary's share was ROLLED OVER into an inherited IRA on November 1, 2016. The custodian of the new inherited IRA did not indicate any RMD was due for 2016, nor did the custodian of the original IRA. Should there have been an RMD made in 2016 for this inherited IRA ROLLOVER account?
IRA custodians are not required to inform *beneficiaries* that an RMD is required from an inherited account. They are only required to notify account *owners* that an RMD amount must be calculated for that account. The custodian of the original IRA surely would have notified the deceased (before death, of course) of the deceased RMD requirement. IRA custodians also cannot force out RMDs since it may be possible to satisfy an RMD from a different IRA account of the owner.
The remainder of the deceased's 2016 RMD can be satisfied by a distributions from any of the beneficiaries' separate accounts in any combination. If one beneficiary took a distribution in 2016 from their portion sufficient to complete the deceased's year-of-death RMD, that's covers it. If the sum of all distributions taken by beneficiaries in 2016 was insufficient to complete the deceased's RMD, there is a late RMD for 2016 that must be completed. The beneficiaries taking distributions in 2017 to satisfy the outstanding amount should file Form 5329 with their 2016 tax return to request a waiver of the 50% excess accumulation penalty for having now completed the 2016 RMD. These distributions taken in 2017 will be reported as income on their 2017 tax returns along with their 2017 beneficiary RMDs taken in 2017.
There is no "partial year" when determining RMDs; RMDs are calculated as a yearly amount. However, any part of year-of-death RMD required to be taken by the deceased that was not satisfied by the deceased prior to death is the combined responsibility of the beneficiaries. The beneficiaries can satisfy the remainder of the deceased's year-of-death with any combination of distributions paid to the beneficiaries.
Provided that a separate account for each designated beneficiary was established by December 31, of the year following the year of death, each beneficiary will be required to calculate and take their own RMD as beneficiary from their own inherited IRA account. If separate accounts were not established, RMDs are based on the age of the oldest designated beneficiary.
See IRS Pub 590-B regarding the determination of the amount of RMDs:
https://www.irs.gov/publications/p590b/ch01.html#en_US_2016_publink1000230753