Romney's tax returns show most of his $21.7 million income came from his investments. He also gave nearly $3 million combined to charitable causes and the Mormon Church, helping reduce his effective tax rate to about 14 percent.
The former Massachusetts governor has been under pressure in recent weeks to release his tax returns. Rival Newt Gingrich made public his returns on Saturday, showing he paid almost $1 million in income taxes.
One week ago, the campaign for the Republican presidential nominee looked like Romney's to lose. Not anymore.
The next stop for the Republican presidential candidates is Florida. As they head into the first big-state primary, the race appears to be more unsettled than ever.
As the primary gets closer, the campaign rhetoric gets hotter and Florida's outcome becomes even more important to the candidates.
Romney's fall in the polls and loss in South Carolina has brought a new edge to his attacks. He accuses former Gingrich of being a highly paid lobbyist for Freddie Mac.
"You're speaking with congressmen in a way to help that company, that's lobbying. If it walks like a duck and quacks like a duck, it is a duck," said Romney.
Gingrich denies he lobbied anyone.
"He keeps using the word 'lobbyist' because I'm sure his consultants tell him it scores well. It's not true. He knows it's not true," said Gingrich.
Romney is spending millions on new Florida ads to say otherwise.
A new national Gallup Poll gives a reason for Romney's sharp attacks. One week ago his lead was 24 points. Romney led Gingrich 37 percent to 13 percent. Monday they are virtually tied, with Romney at 29 percent and Gingrich at 28 percent.
Romney agreed to release his tax records after constant attacks by Gingrich
"The speaker was very animated about my releasing tax records," said Romney. "I am. I think it's an appropriate observation that people should know if there's going to be an 'October surprise.' And in the case of the speaker he's got some records which could represent an October surprise. We could see an October surprise a day from Newt Gingrich."
Gingrich accuses Romney of lying, and sets his sights on Florida, which next week could be a pivotal contest in the campaign.
"I think my job in Florida is to convince people that I am the one candidate who can clearly defeat Obama in a series of debates and the one candidate who has big enough solutions that they would really get America back on track," said Gingrich.
Gingrich has agreed to answer charges that he's a lobbyist for Freddie Mac. His contract with the agency was released Monday night. It states that he was to be paid nearly $2 million strictly for consulting work.
The Associated Press contributed to this report.