Barclays did not admit or deny wrongdoing, but agreed to a censure.
It had not prevented the information from being altered or destroyed, said Finra.
The bank also failed to keep attachments to some Bloomberg emails between 2007 and 2010, and failed to retain about 3.3 million instant messages sent using Bloomberg terminals between 2008 and 2010.
Once one instant message with an attachment was processed by the bank, no more could be received that day, Finra said.
Brad Bennett, enforcement chief at Finra, said: “Ensuring the integrity, accuracy and accessibility of electronic books and records is essential to a firm’s ability to meet its compliance obligations.”
Barclays was fined $435m in July by the Federal Energy Regulatory Commission for allegedly rigging US energy markets.
It was also warned about a possible £50m fine by the UK-based Financial Conduct Authority in September for a “reckless” deal in 2008 with Qatari investors.