Sergio Ramos, Iker Casillas, Xabi Alonso, Andres Iniesta, Xavi Hernandez and Gerard Pique are, according to El Mundo, some of the players under investigation by the Spanish tax authorities for their use of companies created to hold and manage their image rights.
By receiving income through these companies the players can pay tax at the corporate income tax rate, which is much lower (30 percent in 2014) than the personal income tax rate that applies to their salaries (52 percent in most of Spain, and 56 percent in Catalonia).
As a result of legislation, players are permitted to receive, since 1996, "15 percent of their remuneration in image rights through companies."
However, the tax authorities consider that "the majority of these companies created to manage the image rights do not have any real activity."
They are using that supposed lack of real activity to argue that the money received for "image rights" should be treated as simply salary and subject to the top rate of tax.
While the authorities "for the moment are not considering the existence of tax fraud," they are looking at demanding the players pay "the difference between the corporate tax rate and the personal income tax rate (22 or 26 percent difference) for the last four years."
In Spain, the statute of limitations applies after four years, meaning the tax authorities cannot investigate those years, except in certain situations.
For players on six million euros net a year and with the club picking up the personal income tax bill, they would have a gross income of over 12 million euros a year, and the total demanded by the tax authorities for the last four years would be around 1.6 million euros.
Tax experts consulted by El Mundo said that the tax authorities had changed the criteria under which they judged these situations, and that it appeared to be motivated by an "extreme desire" to increase tax receipts.
To avoid "ruining their image" in the eyes of the public, "the majority of the footballers have preferred to reach a settlement," even though the "tax authorities have been unable to prove that the companies are not in fact carrying out some activity in relation to the image rights of the professional footballers."
In addition to many of the players at Real Madrid and Barcelona, the tax authorities have been investigating players at other clubs, including those at Valencia and Atletico Madrid.
Given the investigations go back to 2009, some players who have now retired have seen themselves receiving a letter from the tax authorities, including Carles Puyol and Michel Salgado, as well as some who are now playing outside Spain, such as David Villa and Fernando Llorente.