Public companies now have a new requirement to follow in accounting for events that take place after a financial statement period ends but before the statements are issued.

The Financial Accounting Standards Board published Accounting Standards Update No. 2010-09 to amend Accounting Standards Codification Topic 855, Subsequent Events, which describes how entities should treat “subsequent events.” That refers to significant events that might be of interest to investors taking place after a financial statement period closes but before results of the period are disclosed to investors and regulators.

The new guidance clarifies which entities are required to evaluate subsequent events through the issuance of financial statements and the scope of the disclosure requirements related to subsequent events. FASB adopted the original standard as Financial Accounting Standard No. 165: Subsequent Events before it was folded into the Codification under Topic 855.

FASB developed the standard on subsequent events along with a proposed new standard on going concerns, to update and clarify accounting requirements that have long been observed under auditing standards. While the subsequent event standard was finalized in May 2009, FASB is still deliberating comments and making changes to the going concern proposal, hoping to provide a revised exposure draft before the end of the first quarter.

In an alert to its clients, PricewaterhouseCoopers said FASB amended the guidance to remove the requirement for filers subject to regulation under the Securities and Exchange Commission to disclose the date through which an entity has evaluated subsequent events. That change is intended to assure FASB’s requirement is consistent with current SEC guidance, PwC said.

The board says the new guidance on subsequent events has the potential to change reporting for both public and private companies, but the nature of any reporting changes will depend on how companies have treated subsequent events under old literature.

The guidance is effective immediately for any entity subject to the requirements of U.S. Generally Accepted Accounting Standards, except conduit bond obligors, who will be required to apply the guidance for fiscal years ending after June 15, 2010.