The presidential hopeful attempted to defend his refusal to release his tax returns, breaking with a tradition of transparency among candidate which dates back over 40 years. Ms Clinton challenged him saying: “You've got to ask yourself, why won't he release his tax returns? And I think there may be a couple of reasons. First, maybe he's not as rich as he says he is.
“Second, maybe he's not as charitable as he claims to be. Third, we don't know all of his business dealings but we have been told, through investigative reporting, that he owes about $650 million to Wall Street and foreign banks.
“Or maybe he doesn't want the American people, all of you watching tonight, to know that he's paid nothing in federal taxes because the only years that anybody has ever seen were a couple of years when had he to turn them over to state authorities when he was trying to get a casino license and they showed he didn't pay any federal income tax…”
At which point, Mr Trump interjected: “That makes me smart”.
He continued to defend his decision not to release his tax returns, saying they are currently the subject of an IRS audit and he will release them upon the audit’s completion.
As Ms Clinton continued to criticise the Republican nominee, suggesting his refusal was suspicious, he retorted: “I will release my tax returns, against my lawyer's wishes, when she releases her 33,000 e-mails that have been deleted.”
Ms Clinton’s use of a private email server has undermined much of her campaign, with Mr Trump using it to justify his moniker for her that she is “Crooked Clinton”.
Donald Trump's most controversial quotes
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The first presidential debate is underway as Ms Clinton and Mr Trump go head to head in a tense televised 90 minute show down.
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