The late lodging of paperwork looks set to scupper David de Gea’s £29 million move from Manchester United to Real Madrid.
Reports in the Spanish media say United filed the documents one minute after the 11pm BST deadline on Monday.
Goalkeeper de Gea’s proposed switch to Spain involved Real’s shot-stopper Keylor Navas moving to United.
Neither side has commented officially on the bungle, although the BBC reported that United have a receipt to prove their paperwork was submitted on time.
De Gea was purchased by United in 2011 for £18 million from Atletico Madrid.