Publication 4895
taxmap/pubs/p4895-003.htm#en_us_publink1000263710Generally, the executor can allocate additional basis under section 1022 (up to the FMV of the property) to property acquired from the decedent that was owned by the decedent at the time of death.
taxmap/pubs/p4895-003.htm#en_us_publink1000263711The basis of property acquired from the decedent can be increased by an allocation of Basis Increase only if and to the extent the property was owned by the decedent at the time of
death.
For information about ownership, see
Rules relating to ownership, in the Instructions for Form 8939.