Sam Altman, president of Y Combinator, at TechCrunch Disrupt New York on May 5, 2014 in New York City. Brian Ach/Getty Images for TechCrunch Sam Altman, the Silicon Valley investor behind the venture-capital firm Y Combinator, has some thoughts about Donald Trump's tax returns.

Tweeting from his personal account on Saturday, Altman said the IRS should drop its audit of the GOP presidential nominee's tax returns "in the interest of citizens being able to make a fully informed choice in this election."

"Even though he can release his returns under audit, and there's precedent for this, it seems like he won't," Altman said.

Trump has refused to release his tax returns, despite it being the customary move for modern-day US presidential candidates. The real-estate businessman and his legal advisers have asserted that because of an ongoing audit, he will not release them publicly until the audit is complete — which is not expected to happen before the November election.

High-profile figures in politics and in business have scoffed at the notion that Trump is unable to show the public his tax returns.

The 2012 GOP nominee, Mitt Romney, called the move "disqualifying." Warren Buffett suggested that Trump is "afraid" to release his returns. Entrepreneur and Dallas Mavericks owner Mark Cuban implied that Trump isn't budging because the Clintons "made more" money than him.

In his tweets, Altman argued that if the IRS drops its Trump audit, the New York businessman would be forced to make a move, "so if he doesn't," Altman said, "it'd be reasonable to assume he's hiding something."

Hillary Clinton. AP

The venture capitalist then turned his attention to Hillary Clinton: "I also think Clinton should release transcripts from her speeches to financial institutions."

Calls for Clinton to show those speech transcripts were ignited by her former Democratic primary rival, Bernie Sanders. The Vermont senator routinely condemned the influence of big banks in politics and attempted to cite Clinton's closed-door speeches as evidence of that.

For her part, Clinton has indicated that she's open to showing the public those transcripts "if everybody else agrees to do it."