Under the financial reporting rule, companies may not report results that depart from Generally Accepted Accounting Principles without saying how such pro forma results differ from GAAP. Additionally, they may not be misleading or in error.

The rules apply expressly to material information that a corporation releases, but which is not measured under GAAP, but which are often issued by companies ahead of a merger in order to give investors an indication of the financial picture of a merger target.

Pro forma reporting proliferated in the late 1990s, especially among dot-com and Internet companies, leading to complaints that companies used it to hide negative and highlight only positive financial results.

The five-member SEC also approved a rule that bans corporate executives from trading company stock during pension fund "blackout" periods for employees. Exemptions to this rule cover transactions that were "set up in advance or outside the executives' control," said Alan Beller, director of the SEC Division of Corporation Finance, such as gift stock.

The SEC also passed a rule requiring corporations to disclose whether they have adopted a code of ethics that applies to certain of its senior officers, and whether a financial expert serves on the company's audit committee. If they have not adopted these two things, they must publicly disclose why not.

In an SEC meeting next week, the commissioners expect to consider rules on auditor independence, off-balance-sheet ventures disclosure, mutual fund disclosure, and corporate lawyer conduct.

Congress set a deadline of Jan. 26 for implementing many of the major reforms in the Sarbanes-Oxley law.