West Ham have been fined £115,000 by the Football Association after being found guilty of two charges relating to crowd disturbances during their Carling Cup victory over Millwall.
The Premier League club have also been ordered to pay adjusted costs of £5,000 - but they escaped being forced to play matches behind closed doors.
The violent clashes on August 25 led to 64 arrests and the stabbing of a Millwall fan outside Upton Park, and there were pitch invasions during the match.
West Ham were found guilty of two charges: failure to ensure their supporters refrained from violent, threatening, obscene and provocative behaviour, and failure to ensure their supporters did not enter the field of play.
The club were cleared of the more serious allegations of racist abuse and missile throwing during last week's three-day hearing.
The FA confirmed the penalty after reconvening this morning to hear and consider West Ham's plea of mitigation.
The club have 14 days to appeal the decision upon receipt of the commission's full written judgement.
The FA announced the decision in a statement, which read: "An Independent Regulatory Commission has today fined West Ham United FC having found them in breach of FA rules earlier this week.
"The club has been fined the sum of £115,000 and ordered to pay adjusted costs of £5,000 for the failure to ensure their supporters refrained from violent, threatening, obscene and provocative behaviour and the failure to ensure their supporters did not enter the field of play.
"The club will have 14 days to appeal this finding upon receipt of the commission's full written reasons.''
West Ham expect to receive the written judgement next week and will not make any public comment until a decision over an appeal has been made.