Difference between buy-out and release clauses
A release clause, simply put, is a clause in a player’s contract which automatically requires a club (subject to qualifying conditions dependent on each individual contract, such as non-participation in the Champions League, a specific date, or a bid from a Champions League club) to accept an offer of a pre-determined amount set out in the contract by the buying club. If the minimum amount is triggered, the player is indeed allowed to speak to the buying club.
A buy-out clause is a different proposition. In Spain, buy-out clauses are mandatorily inserted into every player’s contract, as given by the Real Decreto 1006/1985 of 26 June (For the Regulation of the Employment of Professional Sportspeople).
This has created a tendency in Spain to insert huge release clauses into the contracts of star players. Lionel Messi has a rumoured buyout clause of ?250 million while Cristiano Ronaldo is said to have a buyout clause of ?1 billion. These are not so common in England due to the differences in legal systems and the way in which English courts are likely to look at these clauses, which in most likelihood is to hold them null and void.
A buyout clause, simply put, is the valuation that a club has of a player. If an offer equal to the buyout clause is met by a purchasing club, the selling club must accept the offer and the player may move. The key difference here is that under Spanish law, it is not the purchasing club that makes the payment, but the player himself. It is this small detail that creates a lot of the complications and technicalities involved in triggering a buy-out clause.
Buy-out clauses examined
A buy-out clause, or "cláusula de rescission”, is literally what it claims to be. A player must buy out the pre-determined value of his contract. They had existed in Spain for about 10 years before the landmark Bosman judgement, but post-Bosman, it became a way that nervous clubs thought they could protect themselves against a possible legal and financial meltdown wasn't heading their way with players coming and going as they chose.
The idea here is that when a player signs for his new club, he and the club agree on a set fee, which, if paid, allows the player to leave and his employers cannot prevent that.
Most players, despite earning large sums of money, don’t have £30-40 million to buy out their contracts. This must be provided by the purchasing club, who would transfer the money to the player, who then uses those funds to buy out his contract.