Alex Behring, chairman of the board, said Buffett made "many invaluable contributions" to the company.
That means the overall gain from the company's 1964 initial public offering to the end of a year ago would have shown a per-share increase in market value of 2,404,748 percent, according to the letter, compare to the broader market's gains of 15,508 percent during that time, when including dividends.
The new law cut the corporate income tax rate to 21% from 35%, a change that has seen boosting the earnings of scores of US companies.
"Berkshire's gain in net worth during 2017 was $65.3 billion, which increased the per-share book value of both our Class A and Class B stock by 23 percent", Buffett wrote in a letter to Berkshire Hathaway shareholders that accompanied the company's annual report.
In his much-anticipated annual letter to shareholders, Buffett explained that the company's net gain of $65.3 billion in 2017 was only partly due to his employees' efforts.
Warren Buffett published his annual letter on Saturday, and it came with some of the usual trimmings: sage advice and reflections on the past year's success. "The remaining $29 billion was delivered to us in December when Congress rewrote the U.S. Tax Code", Buffett wrote.
But he said the prices asked for businesses past year "hit an all-time high", and Berkshire will be looking for those available at "a sensible purchase price".
The company's often-impressive pace of acquisitions had slowed past year, he noted, when the prices asked for businesses 'hit an all-time high, ' amid what he called 'a purchasing frenzy'. But only $36bn came from Berkshire's operations.
Here's what to watch for in the latest letter from Buffett, 87, which is set for release online Saturday at 8 a.m.at Berkshire's home page http://www.berkshirehathaway.com/. That was almost double the previous year's $24.1 billion, or $9.76 per B share, because of the effects of the tax law.
Net earnings per Class A equivalent share attributable to shareholders jumped to $19,790 from $3,823 a year ago. Real-time viewership in 2017 was about 3.1 million, a gain of 72 percent over the previous year, Buffett said. And it holds major investments in such companies as Coca-Cola Co., Apple and Wells Fargo & Co.
Berkshire's overall performance was hurt by an after-tax $2.2 billion loss in its insurance underwriting unit, which had to pay out large claims following Hurricanes Harvey, Irma and Maria, as well as for quake victims in Mexico and people hurt by California's wildfires. Berkshire's "A" shares also became the first stock ever to reach a price of $300,000.
Buffett urged investors to stick with stocks even though they can be riskier in the short-term.