Warren Buffett refutes Donald Trump's debate claims about his taxes

If you want to call out billionaire Warren Buffett, you'd better bring the receipts, as Republican presidential nominee Donald Trump learned Monday morning. 

In the second presidential debate Sunday night, Trump defended his decision to write off a nearly $1 billion loss — and avoid paying federal income taxes — by saying that Buffett had also taken a "massive deduction." 

That didn't sit too well with the so-called Oracle of Omaha, who clapped back in no uncertain terms with the following statement to CNBC. 

Writing that Trump "has not seen my income tax returns," Buffett then detailed all the tax deductions he took this year, the vast majority of which were for charitable contributions. 

"My deductions totaled $5,477,694, of which allowable charitable contributions were $3,469,179. All but $36,037 of the remainder was for state income taxes," Buffett wrote, noting that he has "paid federal income tax every year since 1944, when [he] was 13." 

This is a burn for two reasons: First, there seems to be little evidence to support Trump's claim that he has given millions of his own dollars to charity.

Second, Buffett's deductions are very different from the tax maneuvers Trump may have used to reduce or eliminate his tax burden.

Indeed, last week the New York Times published a leaked excerpt of Trump's 1995 tax return, which showed the real estate developer declared a $916 million loss: Under existing tax rules the real estate developer would have been allowed to "carry forward" that loss, thus avoiding federal income tax on nearly $50 million in yearly income for 18 years. 

Buffett said that he has kept copies of "all 72" of his tax returns, and that — notably — "none uses a carryforward." 

The third richest man in the world — and supporter of Democratic presidential nominee Hillary Clinton — is no fan of Trump. In an August speech reported by MSNBC, Buffett questioned Trump's "sense of decency" regarding his failure to release his tax returns and his remarks about Humayun Khan, a U.S. serviceman who was slain in Iraq. 

Like Trump, Buffett's taxes are also under audit, his statement to CNBC revealed — a fact that Buffett pointed out created "no problem" in his decision to release information about his own tax payments.

Trump has long insinuated that he can't release his tax returns until his audit is over — a claim the IRS says is untrue.