The Financial Conduct Authority finalised the rules meant to boost diversity among leaders of UK-listed organisations, including a requirement that companies’ boards comprise at least 40 percent women.

The boards of the thousands of companies listed on the FCA’s registrar, which includes fashion purveyors Burberry, Asos and JD Sports, will also need to have at least one ethnic minority. At least one senior position at such organisations — including chief executive officer, chief financial officer or senior independent director —  should be filled by a woman.

Companies are required to report this information to the FCA and “disclose against targets … making it easier for investors to see the diversity of their senior leadership teams,” the FCA said. Companies that do not meet the requirements must “explain why not,” the financial watchdog said.

The rules will apply to listed companies for financial accounting periods starting Apr. 1. The FCA said it will allow some flexibility for smaller firms or those based overseas and companies get to decide how best to collect data to show they are meeting the targets.

Learn more:

UK Retail Is Failing on Diversity Measures, Report Shows

Fewer than 10 percent of chief executive officers in retail are women, while fewer than 6 percent of executive committees have Black or ethnic minority representation, according to the survey carried out by the British Retail Consortium, the executive search firm MBS Group and consultancy PwC.