The document, which is dated December 8, 1980, is likely one of the last things Lennon signed before his death.
Sent to the late-Beatle by accountant Barry Nichols, the letter lists three people as Lennon's proxy voters, giving them permission to vote at the Apple Corps Limited Annual General Meeting, which was due to take place in London later that month.
Lennon was ambushed and shot in the head outside his home on the Upper West Side of Manhattan just before 11 p.m. on Dec. 8, 1980. He was pronounced dead at nearby Roosevelt Hospital.
Lennon's killer was denied parole last month for the 12th time.