Deutsche failed to properly report 29,411,494 Equity Swap CFD (contracts for difference) transactions between November 2007 and April 2013.
The failure, which affected all Deutsche's Equity Swap CFD transaction reports in this period, breaches FCA rules on transaction reporting.
The FCA said the size of the fine reflects the "very significant number of misreported transactions". Deutsche agreed to settle at an early stage of the investigation, and received a 30% reduction of their fine.

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Tracey McDermott, the FCA's director of enforcement and financial crime, said: ''Effective market surveillance is critical to maintain the integrity of our markets and depends on accurate and timely reporting of transactions.
"Deutsche is a major market participant responsible for reporting millions of transactions every year.
"We have repeatedly highlighted the importance of accurate transaction reporting and taken enforcement action against a number of firms.
"There is simply no excuse for Deutsche's failure to get this right. Other firms should be in no doubt about our continued focus on this issue.
"Where the FCA sees any evidence of firms not acting properly we will not hesitate to act."
She said the FCA's overall objective is to ensure that markets work well and with integrity, adding that accurate and complete transaction reporting by firms is an essential tool in delivering this objective.
The FCA uses these reports in a number of ways – including identifying and investigating suspected market abuse, for example insider trading and market manipulation.
Officials said they were "particularly concerned" because they have provided "extensive guidance" to firms on how to submit and check these reports, have already taken action against several other firms, and previously issued Deutsche with a private warning in relation to other similar transaction reporting failures.