Prior to Chubb, Buffett's reliance on confidential filings was rare. In 2020, he used this tag to quickly build multibillion-dollar positions in telecom titan Verizon Communications and integrated oil and gas giant Chevron , the latter of which remains one of Berkshire's top-five holdings by market value. A decade ago, he also used a confidential filing to build up a stake in Phillips 66 .

The all-important question is: Which stock(s) is Warren Buffett buying?

Though there's no way to know this without direct word from the Oracle of Omaha himself or via Berkshire's 13Fs, there are some clues that allow for educated guesses to be made.

The Oracle of Omaha left us some clues about the secret stock he's buying for Berkshire

The biggest clue of what Berkshire's head honcho is up to can be found in Berkshire Hathaway's first-quarter operating results. On page 8, under "Investments in equity securities," you'll see a cost basis comparison between Dec. 31, 2024 and March 31, 2025 for three categories:

The decline in financials directly corresponds to Buffett's ongoing selling activity in Bank of America and the jettisoning of Citigroup stock. Meanwhile, the bulk of the cost-basis increase in consumer products can be explained by Berkshire acquiring approximately $1.1 billion worth of Constellation Brands in the March-ended quarter. Thus, Buffett's confidential stock must reside in the "commercial, industrial and other" segment.

Since we don't know the specific cost bases of most Berkshire investments, I "guestimated" (technical term here, folks) the average share price during the first quarter of the commercial and industrial companies Buffett's company bought and sold. For example, I came up with Berkshire spending roughly $285 million to add to its stake in Pool Corp. , along with around $36 million for Occidental Petroleum and approximately $21 million for HEICO .

Based on this data, it suggests Buffett spent north of $1.6 billion piling into this secret stock during the first quarter. Given that Berkshire would have to report stakes in excess of 5% of all outstanding shares in a company, this signals that Berkshire's confidential stock is a large company -- likely in excess of $50 billion in market cap.

The last tidbit of information we get is Warren Buffett's unwavering desire to get a good deal. He's such a diehard value investor that he's gone cold turkey on buying back shares of his own company for nine consecutive months after spending nearly $78 billion to repurchase shares spanning 24 quarters (July 2018 – June 2024). You'd need to be looking for a company with a clear price dislocation amid a historically pricey stock market.

This could very well be Warren Buffett's confidential treatment stock

Admittedly, there are some broad-stroke assumptions to make here. For instance, while technology is encompassed under "other," Buffett isn't exactly tech savvy, which makes this sector highly unlikely. The same can be said for the healthcare sector.

Furthermore, taking into consideration how consistently Berkshire's chief has added to "indefinite" holding Occidental Petroleum since the beginning of 2022, I'd shy away from the idea that it's another drilling company that's caught his attention. I believe this narrows things down even further to the industrial sector.

President Donald Trump's tariff-induced market sell-off during the first quarter created a number of potentially intriguing entry points in industrial stocks for Buffett. The problem is there are three dozen industrial companies with market caps north of $50 billion, so it's a bit hard to really narrow things down... until you get into valuation .

Only three industrial stocks have forward price-to-earnings (P/E) ratios below 15, which would be a minimum line in the sand for "value" and price dislocations in the current market:

The one factor that keeps me from thinking it's Paccar is simply the company's share price, which has rocketed higher over the last three years. Thus, my thought process leads me to believe Buffett is intrigued by a big-time logistics player.

While FedEx is, currently, the cheaper of the two, based on forward P/E, it's UPS -- a former Berkshire Hathaway holding -- that checks all the right boxes for Berkshire's chief.

UPS stock was absolutely clobbered in late January when the company outlined plans to reduce its volume with its top customer, Amazon (NASDAQ: AMZN) . Though this might sound a bit perplexing given the volume Amazon's online marketplace can generate for a logistics giant like UPS, it makes perfect sense if you focus on the company's longer-term vision. Whereas Amazon's deliveries are generally low-margin, UPS aims to focus its attention on higher margin services. In other words, you have a clear price dislocation due to a short-term concern that doesn't alter UPS's long-term growth prospects.

UPS also offers a sustainable competitive edge given its well-known brown trucks and its network that no other logistics company has matched. Few things excite Buffett more than a price dislocation in a brand-name business with a moat.

The cherry on top is that UPS has a hearty capital-return program. It returned $5.9 billion to its shareholders last year through dividends and share repurchases, and has a dividend yield of 6.5%!

When Buffett sold Berkshire's remaining UPS stake in 2023, shares of the company were hovering in the $170s or $180s. As of this writing, shares are trading hands for around $100, which is a level last seen consistently more than five years ago.

If I had to guess which company is the secret stock Warren Buffett is buying, I'd wager on a reunion with UPS.

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John Mackey, former CEO of Whole Foods Market, an Amazon subsidiary, is a member of The Motley Fool's board of directors. Citigroup is an advertising partner of Motley Fool Money. Bank of America is an advertising partner of Motley Fool Money. Sean Williams has positions in Amazon and Bank of America. The Motley Fool has positions in and recommends Amazon, Bank of America, Berkshire Hathaway, Chevron, Domino's Pizza, and FedEx. The Motley Fool recommends Constellation Brands, Heico, Occidental Petroleum, Phillips 66, United Parcel Service, and Verizon Communications. The Motley Fool has a disclosure policy .

Warren Buffett Is Buying a Secret Stock Again -- and Based on Clues, This Is the Company I Believe He's Building a Position In was originally published by The Motley Fool