Seidman & Seidman, the country's 13th-largest accounting firm, was censured yesterday by the Securities and Exchange Commission and ordered to institute remedial procedures in its auditing practices.

The action, which is just one of a number brought recently against major accounting firms, came as the result of the New York firm's alleged improper conduct in the 1983 audit of Chronar Corp. of Trenton, N.J., the SEC said. The auditor issued an unqualified opinion of Chronar that recognized revenue that the SEC claimed not only had not been earned but also might never be collected. The treatment resulted in a much more favorable financial picture for Chronar.

According to the SEC, the reporting of overstated revenue, representing $1.8 million, or 81 percent, of the company's total revenue, occurred prior to a planned (though never completed) public offering of Chronar securities.

The SEC alleged that Seidman & Seidman had not followed generally accepted accounting principles. Moreover, the order said the firm accepted Chronar's word on the anticipated revenue and gathered no documentation to support it.

The SEC ordered the firm to revise its auditing policies and submit them for review to the agency within 60 days. Gary Lynch, the SEC's director of enforcement, said the job would "require a significant amount of effort" by the firm. Seidman & Seidman consented to the order without either admitting or denying the charges.

Richard Meyer, the firm's counsel, said, "We felt that the issues involved concerned judgments made by our people in good faith. However, we felt that it was prudent to settle the matter and put it behind us."

Seidman & Seidman was founded in 1910 by the forebears of William Seidman, who the White House has picked to be the next chairman of the Federal Deposit Insurance Corp. Seidman severed all financial connections when he left to work for the Ford administration in 1974. Seidman's nomination was sent to the Senate floor last night.