In recent weeks, the FSA has come down hard on corporate corruption
The UK's Financial Services Authority (FSA) has fined three firms a total of £4.2m for failing to provide reports that are used to detect market abuse.
The FSA fined Swiss investment bank Credit Suisse, market maker Getco Europe and broker Instinet Europe.
"(The firms) committed multiple breaches that resulted in failure to provide transaction reports promptly and correctly," the FSA said.
Two of the firms told the BBC that they "regretted" the breaches.
The data is used to detect and investigate suspected market abuse. This includes insider trading and market manipulation.
The FSA said that each firm could have prevented the breaches by carrying out regular reviews of their data. But they failed to do this, "despite repeated reminders".
In response, Richard Balarkas, president of Instinet Europe said:
"We regret the breeches and they've been fixed. We have fully co-operated with the FSA and we're moving on."
In a statement, Credit Suisse also expressed regret in relation to the breach of its transaction reporting obligations.