According to this page, the record is 113,739.9 feet. That's about 18 miles. The reference is to a 1961 flight. I'd be surprised if no one has bested it.
He parachuted back to earth in a supersonic freefall.
https://youtu.be/FHtvDA0W34I
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that’s so odd, when I goggled it earlier it gave me that number, but it appears the record is actually much higher like you said, but still much lower than Branson flew today.