Manchester City are set to owe the Premier League tens of millions of pounds in compensation for legal costs after being found guilty of virtually all charges brought against them.

The Premier League announced on Tuesday that an independent commission had determined the club had artificially inflated their income by £900m over a nine-year period. The panel concluded that Manchester City had arranged “sham” contracts to boost revenues to comply with spending rules.

During the procces both sides racked up what many legal experts predict will be more than £100m in costs between them. Manchester City employed Lord Pannick KC, one of the country’s leading lawyers who has advised the former prime minister Boris Johnson, while the Premier League’s team was spearheaded by Adam Smith KC, considered one of the finest sports lawyers of his generation who has represented the league, the Football Association and Uefa in a series of cases.

The Premier League’s costs are expected to be upwards of £70m and lawyers have told the Guardian that a winning party can expect to recoup around 70% of their legal costs from the losers. That means the league could be awarded almost £50m in compensation for a case that has lasted eight years already and is still not concluded.

In a 40-page document, the independent panel explained why it found Manchester City guilty of all charges related to serious breaches of the Premier League’s financial rules and “the majority of charges in relation to its failure to cooperate with the league’s investigation”.

The commission will rule on the compensation figure once the process has been completed. Manchester City maintain their innocence, claiming in a statement that “a comprehensive body of irrefutable evidence exists”, and intend to appeal, describing the ruling as an “opinion” that contains “clear material errors, of law, principle and fact, and is unsafe”. The club’s chief executive, ­Ferran Soriano, sent a three-minute video to club employees describing it as a “Premier League conspiracy theory”.

The commission will determine if the Premier League’s legal spending was proportionate to the case. After Everton were found guilty of profit and sustainability rule breaches in 2024, the league pushed for £4.9m in costs, but was awarded £1.7m after the club’s lawyers successfully argued the legal costs were too high. Everton lawyers had claimed the cost per document disclosed was 19 times higher for the Premier League than the club, while the cost per witness statement was five times more.

The Premier League declined to comment. Manchester City did not respond to a request for comment.