Release Clause- The release clause is a special optional clause that can be inserted into any new contract that is signed by a player. It can be inserted if the player's agent and the chief negotiator of the signing or re-signing club mutually agree to it. The release clause can be valued anywhere from £10 to £1 billion, depending on the player's age, potential, talent and interest from other clubs. If the release clause for a player is triggered by a certain club, the club does not have to negotiate with the selling club and only has to negotiate personal terms such as a new contract with new terms and a higher salary. A recent example of this would be Thomas Partey. Until last season, he was a player for Atletico Madrid but was heavily pursued by Arsenal who failed to complete a deal for him until the transfer deadline, when they agreed to trigger his release clause and pay Atletico Madrid the full 50 million to sign him.
Buy-back Clause- A buy-back clause in a player's contract is for the selling club to have some security where they can repurchase the player for a certain fee if they excel at the club that purchased them. This clause is beneficial for the selling club because they receive a transfer fee for a player who may not be getting much game time at the club because he is a young player with potential, or if the club has decent squad depth in that position and do not require his services at that time. They can then buy the player again if he plays well at the new club. It is beneficial for the buying club because they are able to buy a player whom they may not have been able to buy had it not been for the clause, and also the fact that the buy-back fee is almost always higher than the initial transfer fee, so the club makes a profit on him if/when the clause is triggered. It's also beneficial for the player because they can display their talent elsewhere while getting regular playing time, along with building their reputation.
First Refusal Clause- A first refusal clause is where the club from who the player left, is informed of the fact that the player is being sold on put on the transfer list. The club then has the power to decide whether they want to buy that player again, or if they don't want to. An example of this clause is in Olympique Lyonnais' forward Memphis Depay's contract when he was at Manchester United. It has a first refusal clause, so if Olympique Lyonnais decide that they want to sell Memphis Depay, Manchester United get the first say on whether or not they want to buy the player before he is offered to other interested clubs.
Percentage of next sale clause- Teams will also lock in a percentage of the next deal by football contract provisions before trading a player. When they make their next move, they are then entitled to a particular number of the player's next transfer fee. In the contracts of young players who can or may not reach their success in the competition, it is a worthwhile clause to insert.