Liverpool were fined £200,000 ($246,000) by the English Football League on Wednesday after fielding an ineligible player in their League Cup win at Milton Keynes Dons.
Spanish midfielder Pedro Chirivella featured as a substitute for Liverpool after coming on for the last 28 minutes of the 2-0 third-round win last week.
Chirivella, who had been on loan at Spanish club Extremadura last season, was not registered to play for Jurgen Klopp’s side at Stadium MK.
Liverpool had not secured an international transfer certificate, which was required after the 22-year-old’s return to Anfield following his loan.
It was suggested Liverpool could be kicked out of the League Cup as punishment.
But instead Liverpool have been fined, with £100,000 of the penalty suspended.
“Following a comprehensive review of all the evidence, the board determined that it wasn’t appropriate to expel the club from the competition because of a number of mitigating factors,” a Football League statement said.
A Liverpool club spokesperson said: “The club accepts the judgement, outcome and punishment imposed by the EFL.
“We believe it is proportionate with the technical indiscretion committed and will be making no further representations.
“Even though there were mitigating factors, which were beyond our control or jurisdiction, we believe it appropriate we apologise to the competition’s governing body and also to Milton Keynes Dons.”
Liverpool requested the paperwork in July but the process can only be completed with the English Football Association’s intervention.
It is believed that is where the Champions League holders think the error has been made.
“In particular, the board noted that the club had sought the assistance of the Football Association in securing the return of the international clearance prior to the start of this season,” the statement said.
Liverpool would be liable to pay the suspended £100,000, plus face an additional sanction, if they fielded an ineligible player again in the League Cup before the end of next season.