Hampden, the Lloyd's managing agent, has been fined £10,000 by regulators after admitting to a charge of misconduct.
The Lloyd's disciplinary board decided the member's agent contravened their coming-into-line requirements to gain membership.
Those underwriting for last year's account needed a certain level of funds by November 1999.
Hampden, which signed the Member's Agent Confirmation Form later that month, said all its members had met those requirements or sought time extensions from Lloyd's.
But one of its corporate members did not provide the necessary funds and three others failed to give increased letters of credit until December.
In addition, they had not asked Lloyd's for extra time.
Hampden has now been ordered to pay a £10,000 fine and £500 to cover Lloyd's costs.
Nigel Hanbury, managing director of Hampden, said: “We have a huge number of deadlines and through a clerical error, four were not properly in line by the due date, but before the year end.
“We have deadlines and they must be met so we will be paying the fine,” he said.
A spokesman for the Lloyd's disciplinary board said: “At the time of signing the confirmation form, Hampden knew or ought to have known that the information contained in that form was incorrect, in that four of its members had not complied with the coming-into-line requirements nor sought an extension of time in which to do so.”