Cardiff face a three-window transfer ban unless they pay the first instalment of the transfer fee for Emiliano Sala to Nantes.
The Argentinian, 28, died when the light aircraft he was travelling in from France to the UK crashed into the English Channel on January 21 of this year.
Championship club Cardiff and Nantes were unable to reach an amicable conclusion on the financial aspects of the move, so the case came before the players’ status committee (PSC) of world governing body FIFA.
It was announced by FIFA on September 30 that Cardiff had been ordered to pay the first instalment of Sala’s transfer fee – €6 million euros ($A9.7 million).
After getting the written verdict in recent days, the Welsh club can appeal against FIFA’s ruling at the Court of Arbitration for Sport.
FIFA says an appeal will stop the clock on the 45-day deadline to pay until a binding verdict by CAS. That could take about one year.