For years, Warren Buffett's Berkshire Hathaway has been one of the biggest owners of Apple common stock.

At the end of 2023, Berkshire  (BRK.A)  owned 907.6 million, or 5.7%, of Apple's  (AAPL)  shares outstanding. At the time, the shares were valued at an estimated $174.3 billion.

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Early this year, Berkshire Hathaway started to sell its Apple shares. As of Sept. 30, it had cut its stake by two-thirds.

It still has about 296 million Apple shares if you work the math in Berkshire's  (BRK.B)  third-quarter-earnings report.

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The quarterly report, released Saturday, valued the Apple holding on Sept. 30 at $69 billion, or about $233 per share.

Berkshire Hathaway has more than $320 billion of cash before taxes right now, a third of its total net worth, which it can deploy at any time. It can buy companies, it can buy stocks, it can retire its own shares.

The cash hoard also includes the proceeds from its sale of $9 billion of Bank of America  (BAC)  shares.

Buffett and the art of when to sell a stock

Berkshire Hathaway is not obligated to report all the trades it has made to reduce its Apple position.

In theory, selling the shares should reduce the stock price because more shares are on the market.

But the sales appear to have been done so carefully that Apple's share price rose from $192.53 on Dec. 31, 2023, to $233 by the end of the third quarter. For the year, Apple is up 15.8%.

Buffett won, and so did Apple holders.

Why is Buffett selling Apple stock?

Apple shares are rising and sport a 15.8% gain on the year. Plus, the Cupertino, Calif., tech giant has the world's top market capitalization: $3.37 trillion.

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At Berkshire's annual meeting in May, Buffett himself cited tax concerns were playing a part. Berkshire's financial reports suggest its cost basis (what it paid for the shares) was $19.1 billion.

Berkshire made only minor adjustments to its stake over the years after assembling its position. It was Apple's third-largest holding.

So, potentially, Berkshire had then, and undoubtedly still has, a large capital gain on its books.

But even last spring Buffett thought Apple shares were getting too rich.

Don't pay too much for any stock

Another reason: Buffett and his investment managers are firm believers in buying what the late Charlie Munger, Buffett's great friend and closest adviser, once called "great companies at a great price."