West Ham believe they have signed Blackburn Rovers right-back Lars Jacobsen, but did not fax the Premier League until two minutes before the transfer window closed.
With the Premier League having to deal with a backlog of late signings, the Hammers were left waiting to discover whether the transaction was registered on time.
It is understood that West Ham have agreed to sign the defender on a loan deal, with an option to make the deal permanent if he impresses at Upton Park.
Jacobsen joined Blackburn from Everton last summer and started 11 games in the Premier League last season. The 30-year-old appeared in all three of Denmark's games at the World Cup finals.
Blackburn have also sent midfielder Alan Judge on loan to Notts County while Maceo Rigters has joined Willem II for the remainder of the season.