Research by ACA Group has detected more than six million transaction reporting costs that it says "expose huge gaps for market abuse and systemic risk monitoring".
The risk specialist found the transaction reporting errors across a sample of 30 review projects averaging 200,000 errors per review.
Some 97% of reports under MiFIR and EMIR regulation contain inaccuracies, according to ACA Group.
Despite this, the majority of firms (87%) have expressed confidence in their reporting, regardless of the errors.
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ACA Group stated that there is evidence suggesting firms "either remain naïve around their reporting obligations, have misplaced confidence of the quality of their reporting, or simply do not know they are in breach".
Matt Chapman, managing director and co-lead of the ACA's Regulatory Reporting Monitoring & Assurance (ARRMA) Service, ACA Group, commented: "The longer it takes firms to realise they have a problem, the more expensive and time consuming it becomes to fix and the more embarrassing the conversation with the regulator becomes."
Charlotte Longman, director and co-lead ARRMA, added: "Over the past year, we've noticed a significant reduction in errors with our clients who have incorporated both technology and specialist consulting oversight.
"This blend has seen firms increase their accuracy, on average, by 95% once the consulting recommendations have been implemented.
"It's vital that firms prepare for increased regulatory scrutiny in the months ahead as the FCA has hinted that it will be combatting persistent reporting failings by taking action against firms which are not taking sufficient action to remedy their errors. With MiFID II recently reaching its four-year anniversary, it's becoming a question of ‘when' and not ‘if' we start hearing about firms being fined or censured."
