

McCartney's manuscript for the song sold for $55,700 (equivalent to US$102,000 in 2021) at Sotheby's, London in September 1994.

We just stuck a few more words on it like 'grandchildren on your knee' and 'Vera, Chuck and Dave' … this was just one that was quite a hit with us." Lennon's contribution of the children's names were likely made in the studio. In 1967, John Lennon said of the song, "Paul wrote it in the Cavern days. Pepper's Lonely Hearts Club Band in December 1966 because his father, Jim McCartney, turned 64 earlier that year. Both George Martin and Lewisohn speculated that McCartney may have thought of the song when recording began for Sgt. It was in the Beatles' setlist in their early days as a song to perform when their amplifiers broke down or the electricity went off. Beatles historian Mark Lewisohn suggests it was McCartney's second composition, coming after " Call It Suicide" but before " I Lost My Little Girl". Although the theme is ageing, it was one of the first songs McCartney wrote. The song is sung by a young man to his lover, and is about his plans of their growing old together.

When I was fourteen there wasn't much of a clue that it was going to happen." In 1987, McCartney recalled, "Rock and roll was about to happen that year, it was about to break, I was still a little bit cabaret minded", and in 1974, "I wrote a lot of stuff thinking I was going to end up in the cabaret, not realizing that rock and roll was particularly going to happen. Paul McCartney wrote the melody to "When I'm Sixty-Four" around the age of 14, probably at 20 Forthlin Road in April or May 1956.
