(Bloomberg) ? American International Group Inc., Calpine Corp. and 355 other US companies are late filing annual reports, three times as many as last year, because of crackdowns on accounting by state and federal officials.

AIG, the world's largest insurer, missed the Securities and Exchange Commission's March 16 deadline for yearly financial statements because the New York-based company faces an accounting probe. Calpine, a California-based power producer, couldn't comply in time with new rules for financial controls.

At least half the companies attributed delays to the Sarbanes- Oxley Act, a 2002 law that added new reporting requirements and forced chief financial officers to attest to the accuracy of financial statements. The law, which increases criminal fines and prison time as much as ten-fold, has been criticised by the US Chamber of Commerce and other business groups for being too costly and complicated.

"It's very difficult to comply with Sarbanes-Oxley and some companies just ran out of time," said Dennis Beresford, an accounting professor at the University of Georgia in Athens. "The SEC is scrutinising every detail now."

A fifteen-day extension on filing annual reports is commonly granted, said Jack Ciesielski, publisher of Analyst's Accounting Observer, a Baltimore-based newsletter. "The real question is, what happens if a company can't file by the end of the month?" Ciesielski said.

Meeting the Sarbanes-Oxley rules cost companies an average of $4.3 million in 2004, more than double company estimates at the beginning of last year, according to a survey of 321 companies released today by Financial Executives International, a group representing chief financial officers and treasurers.

Companies with more than $5 billion in sales spent an average of $10.5 million to comply with the rules, double their January 2004 estimates, said the Florham Park, New Jersey-based financial executives group.

In addition to Sarbanes-Oxley, federal or state accounting investigations prompted many companies to delay their annual reports.

AIG is a target of a probe by New York Attorney General Eliot Spitzer over whether the insurer sold policies that helped other companies manipulate earnings. AIG said its annual report was delayed by management changes and an "ongoing internal review of the accounting of certain transactions."

Maurice "Hank" Greenberg stepped down last week as the company's chief executive. Chris Winans, an AIG spokesman, didn't return a call for comment.

Sarbanes-Oxley's Section 404, which went into effect in November, requires companies to have systems monitoring financial activities, such as payroll and inventory, certified by their auditors.

Some companies didn't get the controls in place, while at others, auditors found weaknesses in the systems and couldn't certify them.

"We needed more time for Sarbanes-Oxley," said Calpine spokesman William Highlander. The company is also assessing the tax impact of closing some Canadian operations, he said.

Delphi Corp., the world's largest auto-parts maker, said it delayed its annual report because it has to restate three prior years' profits after a company probe found inflated cash flow and pretax income for some periods. The company said it may take until June to complete the restatement.

"The jump in the number of companies who cannot prepare and file their annual reports to investors on time is a strong indicator of just how poor controls and financial management are today," said former SEC Chief Accountant Lynn Turner.

Blockbuster Inc., the largest US video rental chain, was one of 12 companies that delayed annual-report filings because the SEC said they might be understating rents and improvement costs on store leases.

"We are reviewing the leases of 7,000 company stores worldwide," said Randy Hargrove, a Blockbuster spokesman. "It takes considerable time and resources, so we are filing late." The company will complete its review by the end of the month, Hargrove said.

SEC Chairman William Donaldson said in a speech on March 16 that he expected companies in coming months to say they were unable to finish audits of internal financial controls on time. "In those cases we are looking for clear disclosure by companies," Donaldson said.

Matt Well, an SEC spokesman, declined to comment beyond Donaldson's speech.