David De Gea's transfer to Real Madrid has reportedly collapsed because the paper work was not submitted on time.
United were looking to bring in Keylor Navas from Madrid, as well as receive £18m as part of the deal, however it now appears to have fallen through.
Neither club has made an official announcement on the details.
However, Spanish media are reporting that United are responsible, as the club did not send the paper work by the deadline time.
But Manchester claim they have a receipt which proves that the documents were indeed sent on time and are holding Real responsible for the deal collapsing.
Sky Sports are reporting that FIFA will hear an appeal from both clubs tomorrow, in a last ditch attempt to get the deal through.