Fifa have rejected Barcelona's appeal against a one-year transfer ban which will now come into effect in January 2015.
The world football governing body imposed the sanction in April after Barça were found to be in breach of the signings of 10 minor players but it was lifted, pending an appeal.
Barça have since spent £120 million on Marc-André ter Stegen, Ivan Rakitić, Luis Suárez, Claudio Bravo, Jeremy Mathieu and Thomas Vermaelen this summer.
"FC Barcelona is to serve a transfer ban which will see the club prevented from registering any players at both national and international level for two complete and consecutive transfer periods, starting with the next registration period (January 2015) given that the appeal of the club had been granted suspensive effect by the chairman of the FIFA Appeal Committee. FC Barcelona has also been ordered to pay a fine of CHF 450,000 and been given a period of 90 days from today in which to regularise the situation of all minor players concerned.
Meanwhile, the RFEF has been ordered to pay a fine of CHF 500,000 and granted a period of one year in which to regularise their regulatory framework and existing system concerning the international transfer of minors in football."
Barcelona can not strengthen their squad in either the winter January transfer window nor the three-month summer window next year.
Their appeal prevented potentially huge ramifications for the squad, after club icon Carles Puyol and goalkeeper Victor Valdés departed following a turbulent campaign. Instead, new coach Luís Enrique has bought the aforementioned six players and sold Cesc Fàbregas and Alexis Sánchez.
Barcelona won just the Supercopa in 2013-14, as former president Sandro Rosell resigned over the allegation he misappropriated funds from the signing of striker Neymar, which the club was charged with tax fraud over.Suggest a correction