Warren Buffett's Berkshire Hathaway saw its net worth surge by $65 billion in 2017, almost half of which came from tax proceeds from the recently passed GOP law.

There's an expectation that financial services firms will be among the market's biggest beneficiaries of tax reform.

The recently passed GOP tax law has been kind to Warren Buffett's Berkshire Hathaway, to say the least.

"A large portion of our gain did not come from anything we accomplished at Berkshire," Buffett wrote.

The firm's most recent annual letter revealed the investment conglomerate's net worth surged $65 billion in 2017, with $29 billion of that stemming from tax proceeds. That gain was realized in December, after the passage of the tax plan.

In a client note leading up to the letter's release, Morgan Stanley estimated the tax law could boost Berkshire's book value by as much as $37 billion. And while the company didn't quite reach Morgan Stanley's lofty expectations, it still realized an enormous windfall.

The tax law's positive effect on Berkshire's net worth helps confirm the widely-held expectation that financial services firms will be among its biggest beneficiaries.

Business Insider will be covering the letter in full on Saturday. Follow our coverage here.