Donald Trump. AP Photo/Evan Vucci LinkedIn cofounder Reid Hoffman is now throwing his weight behind the mounting pressure on Republican candidate Donald Trump to release his tax returns.

In a Medium post on Monday, Hoffman said he would give up to $5 million of his money to veterans if Trump releases his returns before the last presidential debate, slated for October.

Specifically, Hoffman is backing a campaign led by Marine Corps veteran Peter Kiernan on Crowdpac to incentivize Trump to release his returns.

Hoffman is pledging to match $5 to every $1 donated to the campaign, up to a $5 million maximum. In other words, if the campaign raises $200,000, Hoffman will donate $1 million, and so on, up to the campaign's $1 million goal. The money raised between Hoffman and the campaign will be distributed to different veterans charities.

Trump's taxes have been an ongoing topic for much of the year. It is customary for US presidential candidates to show the public their personal tax returns, but Trump has refused to do so, citing an ongoing IRS audit. His refusal has prompted all kinds of speculation about his personal finances.

The way Hoffman sees it, Trump has no reason to keep delaying releasing the returns except for seeing them "as a bargaining chip to utilize" when his campaign needs it, Hoffman writes.

As a result, Hoffman is backing a campaign that gives Trump incentives to release his returns, but doesn't reward him for the act.

"Instead, men and women to whom all Americans owe a great debt of gratitude will benefit from any positive action he takes," Hoffman said.