Noah Berger/Bloomberg via Getty Images LinkedIn co-founder Reid Hoffman says he is willing to donate up to $5 million to charities supporting veterans if Donald Trump releases his personal income tax returns by Oct. 19.

Turning a 2012 political stunt by Donald Trump on its head, LinkedIn co-founder Reid Hoffman said Monday that he’s prepared to donate as much as $5 million to veterans charities if the GOP presidential nominee releases his tax returns.

In a post published Monday on Medium, Hoffman compared his announcement to Trump’s own 2012 offer to donate $5 million to charity if President Barack Obama released his college transcripts and passport records.

The LinkedIn co-founder is essentially turning the tables on Trump, who’s refused to release his personal tax returns, citing an ongoing IRS audit that wouldn’t actually prevent him from releasing the returns if he wanted.

“Trump often says he needs to keep his tax returns private until the IRS finishes auditing him,” Hoffman wrote. “But the IRS itself has said this isn’t necessary. And recently Trump changed his tune, saying he’ll release his returns as soon as Hillary Clinton releases the 33,000 emails she deleted from her email server.”

“What this means, of course, is that there’s no real reason that Trump is keeping his returns secret, except that he sees them as a bargaining chip to utilize,” he added.

In his post, Hoffman told the story of Peter Kiernan, a 26-year-old Marine who’s launched a campaign on the fundraising site Crowdpac. Kiernan hopes to raise at least $25,000 for charities supporting veterans if Trump releases his tax returns by Oct. 19.

With Trump’s 2012 offer to Obama in mind, Hoffman said that if Kiernan’s campaign meets or exceeds its fundraising goal, he’ll match the total fivefold. Hoffman said he is prepared to donate up to $5 million.

“The ingenuity of Kiernan’s proposal is how it gives Trump a strong incentive to act but doesn’t reward him directly for something he should have already done,” Hoffman wrote at Medium. “Instead, men and women to whom all Americans owe a great debt of gratitude will benefit from any positive action he takes.”

Last year, former Secretary of State Hillary Clinton released her personal income tax returns spanning eight years ― 2007 through 2014 ― shortly after declaring her candidacy. Her 2015 tax return, which was released last month, showed that she and her husband, former President Bill Clinton, took in $10.6 million last year and paid $3.24 million in taxes.

Because of Clinton’s 2008 presidential campaign and her husband’s decades-long political career, the couple’s tax returns are available going back to 1977.

If Trump doesn’t make his tax returns publicly available, it will break from a tradition more than 40 years old. Nearly every major presidential candidate since 1973 has released his or her personal returns, with the exception of Gerald Ford, who released a tax summary that covered several years but never made his full returns available.

Editor’s note: Donald Trump regularly incites political violence and is a serial liar, rampant xenophobe, racist, misogynist and birther who has repeatedly pledged to ban all Muslims — 1.6 billion members of an entire religion — from entering the U.S.