Pretty much every transfer is paid over years, normally the length of the contract signed. It’s how the buying club writes off the value of the player
Not true, there is no connection between the payment terms and how the club writes off the value of the player. The transfer value is amortized (effectively written down) over the number of years of the contract term; the payment terms/schedule are completely irrelevant.
Chelsea are the most obvious and extreme exponent of this with their recent 8 year contracts, enabling them to write off the player value over 8 years (and thus minimise their annual PSR exposure).