It tends to be either:- 1. The balance of signing on fees which were spread across the length of the contract; or 2. A payment to compensate for a drop in wages. Number 1 is the Barton scenario eg a player is given a 1m signing bonus spread across the length of a 5 year contract - he gets a 200k lump sum payment in advance for every year he stays. If he is sold against his wishes with 2 years remaining he seeks 400k which is the balance of the money due for being loyal. This si the one that is usually all about whether a transfer request is made or not. Number 2 is the problem Leeds found themselves in eg Fowler, Keane, Mills all got compensated for drop in salary for the remaining time left on their Leeds contracts. This tends to affect us, plus other big clubs, when trying to shift players on to clubs paying them a lower wage. Both of the above are of course able to be settled between player and club to find a mutually acceptable position.