The SEC is likely to propose a new rule next year that publicly traded companies file their financial reports using XBRL, the interactive data language SEC Chairman Christopher Cox has long hailed as a powerful tool for investors to study financial results.

Speaking at a Sept. 25 press conference to unveil a new “taxonomy” of XBRL terms used to classify financial data, Cox said he has asked SEC staff to “finalize a recommendation to the Commission that we could act on next spring, about how to deliver the maximum benefit of tagged data to investors, including converting all public company disclosure ...