April 10, 1970 is the popular answer to the question, and it proved to be correct in practice, but it wasn't the official end of The Beatles. The Beatles were a partnership, and the group didn't officially break up until the partners had agreed on the dissolution of the partnership. Although The Beatles' last recording sessions (without John, who had previously told the others that he was quitting) were in January 1970 and Paul McCartney then announced that the group had broken up on April 10, The Beatles didn't officially break up until that partnership was dissolved. McCartney didn't file the paperwork for the dissolution until December 31, 1970, and a judge ordered the affairs of the partnership put in receivership in March 1971 (which could be argued to be the correct date), but the partnership continued through some more messy disputes over the terms of its termination, Ultimately, terms for dissolution were reached, and a formal signing ceremony in New York was arranged with everyone, including Paul, George, Ringo, Apple, and EMI -- but John Lennon skipped it. Thus, The Beatles weren't officially dissolved until Lennon signed off on the agreement at Disney World (!!) on December 29, 1974. https://ultimateclassicrock.com/john-lennon-ended-beatles-at-disney/