A player whose contract has expired can move without a fee. The absence of a fee does not make the signing inexpensive, and often makes it riskier.
The saving moves rather than disappears
With no fee to pay, the competition for the player is broader, and clubs bid against each other using the only currency left, which is salary.
Wages committed over a long contract can exceed what a transfer fee would have been, and a signing bonus paid at the start replicates much of the up-front cost.
Agents' commissions on free transfers are typically larger for the same reason, since the deal contains no fee from which the selling club's share would be taken.
There is no residual value to recover
A player bought for a fee carries a book value that can be recovered by selling him. A free signing carries none, so the club cannot recoup anything if the move fails.
That converts the wage commitment into a fixed liability. An underperforming free signing on a long contract is difficult to move, because another club must absorb the same salary.
The absence of a fee therefore removes the club's exit route as well as its entry cost.
Age is the usual reason a player is available
Clubs let contracts expire mainly when they judge that a player's remaining years do not justify a renewal at his current terms.
A signing club is therefore acquiring a player its previous employer chose not to keep, which is information worth weighing carefully.
Exceptions exist where a player wants to leave and a club cannot persuade him to sign, but those cases are visible well in advance and attract a crowded field.
Pre-contract rules shape the timing
In many jurisdictions a player may negotiate with foreign clubs once his contract has a defined short period remaining, which allows a move to be agreed months ahead.
This creates a stretch of the season in which a club knows it will lose a player and can neither prevent it nor receive anything for him.
Some clubs respond by selling a year earlier at a reduced fee, accepting less than the player's value in exchange for receiving something.
Training compensation applies to younger players
Where a player moving for free is below a defined age, the clubs that trained him are entitled to compensation calculated from their years of involvement.
This exists so that academies retain an incentive to develop players who might otherwise leave for nothing the moment they become useful.
Above that age threshold the payment does not apply, which is why genuinely free transfers concentrate among established players in the later part of their careers.
