Of course I know the song, but taxes had nothing to do with their breakup.
https://taxfoundation.org/beatles-friend-taxes-helped-break-them
First told to give away vast amounts to avoid tax bills — which they did in a series of madcap ventures, offering money to any old person who dropped by with a demo tape — then told they had to make £120,000 in order to keep just £10,000. Soon their finances were in chaos and their energy sapped, as nutters beseiged Apple HQ pressing tapes on them. They also ran a clothes shop as a tax dodge.
https://www.grunge.com/247829/the-break-up-of-the-beatles-explained/
The greatest source of financial strain upon the Fab Four in the late '60s and early '70s was the company they co-owned together, Apple Corps. Originally set up in 1967 by Brian Epstein as a way, quite frankly, of avoiding tax, the company became a constant source of difficulty for the group.