After each financial quarter, the Securities and Exchange Commission requires all institutional investment companies with at least $100 million in assets under management to disclose their holdings in 13F forms. These filings provide a window into the thoughts and actions of some of the world's most successful financial professionals and companies.

If you're a member of the billionaires' club, you're probably doing something right, so it's little wonder that investors look to these publicly available documents for market insights and worthwhile stock-buying leads. With that in mind, read on for a look at two trillion-dollar companies that billionaires poured money into in last year's final quarter. 

A hundred dollar bill and chart lines.

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1. Amazon

Amazon (AMZN 1.16%) remains one of the most influential companies in the world, but that hasn't stopped its stock from seeing big sell-offs in the face of macroeconomic and industry-specific pressures. The company's share price struggled last year as rising interest rates prompted investors to move out of growth stocks and inflationary pressures elevated costs for its business, but the stock attracted multiple billionaire buyers late last year. 

Billionaire investor Jim Simons heads up Renaissance Technologies and is considered by many to be one of today's most innovative and influential investors. Simons was one of the pioneers of algorithm-based trading and has been called one of the best stock traders to ever live, so it's notable that his hedge fund purchased roughly 8.2 million shares in the fourth quarter of 2022. The purchase increased Renaissance's position in Amazon stock by 260% and made it the fund's second-largest holding. 

Simons wasn't the only billionaire investor to make a big bet on Amazon in the quarter. Point72, which is led by hedge fund manager and New York Mets owner Steve Cohen, purchased roughly 3.2 million shares in the period. The buy increased Point72's stake in the company by 174% and made it the fund's fifth-largest overall holding. 

Even after some recovery this year, Amazon stock still trades down roughly 45% from the high that it reached in July 2021. 

AMZN PS Ratio (Forward) Chart

AMZN PS Ratio (Forward) data by YCharts

With a forward price-to-sales ratio under 1.9, Amazon still looks cheaply valued on a historical basis. Between leading positions in e-commerce and cloud computing, and growth drivers in other markets, it remains one of the strongest businesses in the world. Amazon is now back in the trillion-dollar market cap club, and there's a good chance its valuation will continue to climb. 

2. Apple

It's no secret that Berkshire Hathaway CEO Warren Buffett is a huge fan of Apple (AAPL -0.65%) stock. Apple stands as the investment conglomerate's largest equity position by a huge margin, and the Oracle of Omaha has lavished the tech company with praise. In addition to describing the iPhone maker as one of the core pillars of Berkshire's investment empire, the famously successful investor has also gone so far as to say that the tech leader might be the single-best business he knows of. 

With tech stocks seeing turbulent trading in 2022, Buffett seized the opportunity to add more Apple stock to Berkshire's holdings in last year's fourth quarter. It was one of only four stocks that the company bought in the period, with the others being Paramount Global, Occidental Petroleum, and Louisiana-Pacific

On the heels of the purchase and subsequent pricing moves for stocks, Apple accounts for approximately 39% of Berkshire Hathaway's direct stock holdings. To put Buffett's huge vote of confidence in the company in perspective, Bank of America stands as the investment conglomerate's second-largest holding and accounted for "just" 11% of the company's stock portfolio. 

Buffett's love for Apple stems from the company's profitability and market positioning. Apple's incredible brand strength and penchant for delivering products that resonate with consumers help it generate margins that are the envy of the broader technology hardware space, and the company has also built a supporting software-and-services ecosystem that generates high-margin revenue. 

With a market cap of roughly $2.56 trillion, Apple already stands as the world's largest company, but its long list of strengths and competitive advantages suggests there's still room for growth ahead.