Mark Fleming: Image rights, currency guarantees... player contracts are a complex business

A professional footballer's contract can contain some of the most lucrative and ludicrous clauses in the world of employment.

When Lionel Messi signed a new deal with Barcelona last September, the club inserted a buy-out clause set at a staggering £228m. Going from the sublime to the ridiculous, when one Sweden midfielder joined Sunderland from Valencia in 1999 the club included a clause in his contract that banned him from travelling to the moon.

Of course, most contracts fall somewhere in between and are pretty mundane. The basic 16-page Premier League deal, which was the result of negotiations with the players' union, the Professional Footballers' Association, covers a host of clauses and transactions, the most important of which is the money. Fifa insist all payments to players are clearly set out.

Players get a basic salary every month and may receive additional payments every year, normally in sterling, although that is not compulsory. Any signing-on fee must be staggered over the length of a contract, which is commonly for five years. They can also receive status bonuses, for achieving targets such as staying in the Premier League, winning trophies, achieving European football, and team bonuses, for wins and draws.

Clubs will normally include several individual bonuses for first- team appearances, goals, international caps, loyalty bonuses and so on. Typically, for instance, a young player might sign on a lower salary but with higher bonuses, as an incentive to achieve.

Increasingly clubs use image rights as a way of paying their star names, as it allows for lower taxes. Players can avoid paying the highest tax levels by receiving separate payments for the off-field earnings such as shirt sales and promotional work, which are paid into a company set up by the player. The payments are subject to corporation tax, levied at 21 or 28 per cent. Up to a third of earnings now come from image rights.

Contract clauses also detail the player's responsibilities to the club such as staying fit, accepting treatment and shunning drugs. Sam Hammam added his own twist when chairman at Wimbledon, insisting that players agree to eat sheep testicles in his favourite Lebanese restaurant if they ever conceded four goals in a match.

As the former Dons midfielder Robbie Earle said: "It brought a new meaning to defeat leaving a nasty taste in the mouth, but it was typical of a chairman who, in the nicest way, was mad."