In a letter to Republican Rep. Tim Huelskamp yesterday, Buffett revealed that his adjusted gross income last year was $62,855,038 and that his taxable income was $39,814,784. Buffett said he paid $15,300 in payroll taxes.

Buffett also said his federal income tax bill came to $6,923,494, or 17.4 percent of his taxable income — two points he revealed in a New York Times op-ed in August urging Congress to tax the wealthy more.

He said in an interview that the roughly $23 million difference between his adjusted gross income and taxable income was due largely to deductions he took for charitable giving and local taxes.

The 17.4 percent rate can largely be attributed to two factors: A lot of his income came from investments, which are taxed at a lower rate than wages, and payroll taxes are assessed only on the first $106,800 of wages.

“People who make money with money are getting taxed at a far lower rate than people who make money by their own labor,” Buffett told CNNMoney.

In his letter, Buffett also repeated his offer to release his full tax return if other super-wealthy taxpayers — like News Corp. chief Rupert Murdoch — did the same.

“If you could get other ultra-rich Americans to publish their returns along with mine, that would be very useful to the tax dialogue and intelligent reform,” Buffett wrote.