WASHINGTON, Sept 27 (Reuters) - The U.S. Commodity Futures Trading Commission (CFTC) on Monday said it has filed and settled charges against Refinitiv US SEF LLC, in the agency"s first ever enforcement action against a swap execution facility over reporting violations. Refinitiv, which provides financial data and software to traders, banks and investors, has agreed to pay a civil penalty of $650,000 for failing to report certain swap data for at least 320,000 transactions from February 2016 through August 2020, the CFTC said in a statement. It added that on multiple occasions, the firm either knew or had reason to suspect it was not fully complying with requirements. Refinitiv eventually reported the violations to CFTC, the regulator said. Refinitiv did not have an immediate comment. According to the CFTC order, the company did not admit or deny the CFTC charges. The firm is owned by the London Stock Exchange Group (LSEG.L) and is the largest customer of Reuters News. Thomson Reuters, the parent company of Reuters News, holds a minority stake in the LSE.