Billionaire investor Mark Cuban warned Thursday on CNBC’s “Squawk Box” that Vice President Kamala Harris’ capital gains tax plan would “kill the stock market.”

Cuban said, “What I told them is if you tax unrealized gains, you’re going to kill the stock market, and it’s going to be the ultimate employment plan for private equity because companies are not going to go public because you can get whipsawed.”

He added, “Based off the unrealized gains, I would have had to borrow money and I effectively would have been in hawk just to pay my tax bill instead of trying to run my company and a thousand other reasons. They realize that is the issue. I can’t repeat it enough. Even though she is not directly conflicting the Biden tax plan, to her her value proposition is, we need to tax everybody fairly.”

Co-host Rebecca Quick said, “I appreciate you calling in and telling us what you’re hearing on these fronts, that’s great, but as you said yourself, you can’t speak for the vice president. These are things they’re telling you. Who knows what they’re telling other people. My guess is they’re telling anybody who is donating to them exactly what they want to hear at this point,” she said.

Cuban said, “No, no, no, no. Absolutely, positively not.”

Quick said, “Why do you think they’re telling you the truth and not telling other people other people other things? If they won’t say it publicly. Say it publicly so we can hold you to it.”

Cuban said, “I get it, but you’ve got to get the details right.”

Quick said, “Yeah, but we have 60 days until an election.”

Cuban said, “Like any good CEO, you’ve got to do it when you get it right.”

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