Brokers have hit out at the FSA claiming a "lack of transparency" over its fee charging structure.
Richard Adam, director of Lancaster-based Adam & Gaskell, said he had received a request from the FSA for money above and beyond what he expected to pay
Adam argued that calculating the correct fee was unclear.
"I calculated my fees using the formula of a multiple of £3.49 per £1,000 and worked out the correct amount.
"But the FSA came back to me saying the correct amount was £51 more [than my figure]."
He added: "It also said I had under- calculated the stub fee.
"Other brokers have also been told they need to pay supplementary amounts above what they had calculated."
An FSA spokesman said the confusion had arisen because firms also need to take into account a fee of £400 which is charged for firms earning up to £100,000 in annual income, with a range of multiples given for higher incomes in excess of £100,000.
"I can see where this broker is coming from, but the correct way to calculate fees is given on our website and in other information we supply to brokers," the spokesman said.
"Brokers should call our contact centre staff, who will be able to answer any queries linked to fees," he added.
But Adam countered: "I don't think the calculation guidance is clear.
"We are supposed to be transparent but the [FSA's] charging structures are highly confusing."