WASHINGTON — Wall Street’s regulator is putting forward tighter rules on how and when corporate insiders can sell their companies’ stocks, at a time when executives are cashing in at historic levels.

The Securities and Exchange Commission at a meeting Wednesday plans to propose new restrictions on executive stock trading and greater disclosure requirements around company share buybacks. The SEC’s five commissioners are set to vote on the proposal, along with three others. If most support the changes, the agency will put the proposed rules out for public comment before voting to complete them, potentially next year.