SpaceX’s blockbuster initial public offering has raised the prospect of a nearly $2 trillion valuation and IPO windfalls. But it also brings heightened scrutiny to its cryptocurrency holdings—and their sometimes wild fluctuations—under US accounting rules.

Elon Musk’s rocket, satellite, and artificial intelligence company holds more than 18,000 Bitcoin, worth nearly $1.3 billion as of March 31, according to a May regulatory filing. That’s more than twice as much as previously estimated and would rank SpaceX’s Bitcoin stockpile in the top 10 among public companies, according to data from Bitcoin Treasuries.

Once its shares begin trading, …