The ITF, in a full decision of its independent anti-doping tribunal published on its website (www.itftennis.com), said the player was charged with a doping offence in a letter dated June 10 after a positive result in Munich on May 1.
Cilic received the letter on June 11 in London before his first match at the Queen's Club pre-Wimbledon tournament.
The Croat lost the final at Queen's to Andy Murray and, after instructing lawyers, played and won his first-round match at Wimbledon on June 24.
"On 26 June his lawyers in Brussels responded on his behalf, voluntarily accepting a provisional suspension until a decision in the case, and waiving his right to analysis of the B sample," the ITF decision said.
"He withdrew from Wimbledon, citing a knee injury to avoid adverse publicity."
Cilic was quoted at the time as saying it was "a very black day" and the 10th seed's reported injury was one of a spate of withdrawals on the third day that focused attention on the state of the grass courts.
(Reporting by Alan Baldwin; editing by Tony Jimenez)
