Grimsby are the first English club to be fined for breaking coronavirus rules after being found to have committed a number of breaches - including ex-boss Ian Holloway playing darts with his players.
The League Two side postponed three matches in September when midfielder Jock Curran tested positive for Covid-19 and the rest of the squad was forced to self-isolate.
But an EFL investigation found that only two Grimsby players would have needed to self-isolate had social distancing measures been followed, and fined the club £4,880, which is suspended until June.
The Mariners must also foot the £13,000 bill of the EFL probe, as well as covering the costs incurred by the teams they were due to face in the autumn - Cheltenham, Bradford and Hull.
Grimsby were found to have broken the EFL’s Covid-19 protocol by players congregating in communal areas, car sharing and playing darts with Holloway, who quit as boss last month.
‘This should not have happened,’ said furious chairman Philip Day.
’Olly used the playing of darts to build up team ethos and sadly he shouldn’t have done it.
’We’re disappointed because, prior to the players returning to training, we had put in place protocols which were approved by the EFL and we gave a full morning’s training to the staff and players to ensure they were fully conversant with the protocol.
‘The protocols are there for a purpose and they must be complied with.’
News of Grimsby’s sanction comes after EFL chief executive Trevor Birch wrote to all clubs reminding them to ‘vigilantly follow the processes’ to avoid a financially damaging suspension of the season.