Proposed new inflation accounting rules of the Financial Accounting Standards Board would be required of all firms with assets exceeding $1 billion and inventories, plant equipment of more than $125 million. An article in yesterday's editions described these figures incorrectly.

Investors of large public companies may find a new item in annual reports starting in 1980 -- consumer price index averages for five consecutive years, along with data on inflationary impacts on corporate sales and profits.

Inflationary measurements are included in proposed accounting disclosure standards made public yesterday by the Financial Accounting Standards Board, following a study of the issue that started last year.

The proposed changes would be required only for public corporations with inventories, plant and equipment of less than $125 million and total assets of under $1 billion, although other companies would be encouraged to follow the new rules. Most of the nation's 200 largest industrial firms have assets topping $1 billion.

According to Donald J. Kirk, chairman of the accounting board, financial information based solely on historical-cost data "no longer adequately portrays the economic events and position of business enterprises, unless the information somehow can be made to reflect continuing inflation and changing prices."

He told the annual Securities and Exchange Commission conference of the American Institute of Certified Public Accountants here yesterday that information called for in the new rules emphasizes a measurement of assets owned by a business whereas an existing SEC ruling focuses on assets that would replace those owned if replacement took place currently.

If the new FASB statement is accepted after a period of comment and possible public hearings, Kirk said he is hopeful the SEC will withdraw its earlier guidelines.

The proposed accounting rules would be effective for statements of fiscal years ending on or after next Dec. 25, if finally adopted. The new data would be designed to supplement -- not replace -- historical-cost financial statements.

Enterprises involved also would have to provide data on inflation and taxes; the current cost of inventory, property and equipment at the end of a fiscal year; the inflation gain or loss on monetary items; foreign exchange gains or losses and a five-year summary of selected data, including the government's consumer price index.

"Investors and creditors have a need for information on which to base the estimates that are required for investment and lending decisions... there is a need to explain the financial affairs of business enterprises to the general public and those in government who make decisions," the FASB states in its proposal.