Confessions of a Tax Scammer

But now, with three IRS agents by his side, Schneider admitted to ABC that he broke the law. "Today, I'm contrite," he said. "I just want to do what I can to make it right."

Schneider said he has told the IRS everything he knows, and turned over his records, including contact information and transaction details.

'20/20' Exposure

Even after the "20/20" exposé aired, Schneider said that business was booming.

"Believe it or not, people saw your piece and called us and wanted to get involved," he said. "These are people that were very knowledgeable, and had gone the gamut to try and find ways to get out of paying taxes. And when they ran across me, they figured it was a good thing."

Schneider estimates he helped hundreds of clients, from entertainers to dentists, hide millions of dollars from the IRS. And many others paid to hear about his schemes, even if they did not ultimately follow them.

Actress Sandra Bullock acknowledged to "20/20" through her lawyer that Schneider was paid to meet with Bullock's father and lawyers so they could learn more about his scheme. But they say that neither she nor they acted on it nor did anything illegal. Similarly, lawyers for millionaire motivational speaker Tony Robbins say Schneider "may have proposed an offshore banking structure" in discussions with Robbins or his representatives, but said no offshore bank was ever established and no money hidden.

Schneider is now prepared to testify against former clients who did set up banks, despite having told them that everything they were doing was legal.

"I mean, they basically, their own greed motivated them to get out of paying taxes, and they knew that they'd have to face the music one day," Schneider said. "That's the only way that I can make this right is to cooperate with the government and set the record straight."

Having once made millions off his tax-avoidance schemes, Schneider said he is now completely broke and has nothing but regrets.

"I knew all the way along that I was wrong," he said. "And I am paying the price for it now."

Simon Surowicz, Maddy Sauer and Jessica Wang contributed to this report.