Manchester City face a probe by Fifa after Shakhtar Donetsk lodged a complaint about a payment they say they are owed for the sale of Elano.
The Ukrainian club, who sold Elano, 27, to City in 2007, say they are still owed a £475,000 "solidarity payment".
These payments relate to compensation for clubs involved in the development of a player, and usually equate to 5% of the transfer fee.
A Manchester City spokesman declined to comment on the issue.
"We can confirm that Donetsk lodged a claim with Fifa regarding this matter," a Fifa spokesperson told BBC Sport on Wednesday.
"As the relevant procedure will be started in due course, we cannot provide further comments for the time being."
Fifa did not comment on what the potential punishments could be if they ruled against City.
Elano, who was City's top scorer last season with 10 goals, spent three seasons with Shakhtar after joining them from Santos in 2004.
Manchester City's owner Thaksin Shinawatra, who has seen his wife Pojaman sentenced to three years in prison for tax fraud, has had £800m of his personal fortune frozen while authorities in Thailand continue to investigate allegations of fraud against him.
The club has denied that former Thai Prime Minister Thaksin is looking to sell, although a spokesman has admitted that they are holding "exploratory talks" with potential investors in order to raise further finance.
Manager Mark Hughes has also refuted suggestions that players could be sold against his wishes.
City made two signings in the close season, spending £18m to sign striker Jo from CSKA Moscow and signing Tal Ben-Haim for an undisclosed fee from Chelsea.
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