Berkshire Hathaway extensively revised documents related to the acquisition of Wesco Financial at the insistence of securities regulators, according to an April letter made public on Friday.

A series of letters released in the last few months, often months after they were sent, has shown Berkshire and the U.S. Securities and Exchange Commission sparring over the company's accounting and disclosures.

Most of them have related to SEC doubts about the way Warren Buffett's conglomerate accounts for investments that have lost value, but the letter released on Friday has more to do with the adequacy of disclosures to investors.

Berkshire had already owned 80 percent of Wesco for decades when it struck a deal to buy the rest in February. Buffett's business partner and Berkshire's vice chairman, Charlie Munger, ran Wesco and often described the unusual structure of the company as a historical accident.

Accident or not, the SEC had serious questions about the form 13E-3 filed in March related to the deal. By letter on April 4, it raised 23 questions about or objections to various information in the filing.

Berkshire Chief Financial Officer Marc Hamburg responded point-by-point on April 15. In 20 of the 23 cases, he said Berkshire would revise or refile information to reflect concerns raised by SEC staff or clarify information.

Among the items that the SEC asked to be added to or changed were the number of Berkshire Class B shares represented by the merger price, the disclosure on where shareholders could get an updated estimate of the merger value, the disclosure on any financial estimates provided to third parties and the language Berkshire used on forward-looking statements.

Berkshire ultimately filed an amended form on April 18. It was amended again three times in May and once in June before the deal closed.

(Reporting by Ben Berkowitz; Editing by Steve Orlofsky)