At the time Harrison and Starr were both under contract to Northern Songs as a songwriter, and it wasn't until the contract expired in March 1968 that Harrisongs became active. Harrison owned 80% of Harrisongs Ltd, making it potentially far more lucrative for him to publish songs through that company.
Harrison and Ringo Starr received far less money than John Lennon and Paul McCartney for any of their compositions that Northern Songs published due to the way the company shareholdings were distributed. When it was set up in 1963 they owned none of it, but when the company was restructured prior to stock market flotation in 1965 they were allocated 1.6% of the company between them.
Harrison set up another publishing company, Singsong Ltd, on 10 October 1968. The company published just one song, Old Brown Shoe, before it and Harrisongs were combined. Harrisongs then published all of Harrison's later Beatles songs and his early solo works after the group's split.
The headquarters for Harrisongs is at 27 Ovington Square in London, where Apple Corps is also based. It also publishes songs by Harrison's son Dhani's group thenewno2.