Donald Trump’s disclosure that his tax returns have been under review by the Internal Revenue Service for the past 12 years reflects a “very unusual” level of scrutiny by tax authorities, according to a former Internal Revenue Service agent who now works as an accountant for wealthy people.

“He signed his name to a return in which the IRS is finding problems for the past 12 years,” said Alan Olsen, the managing partner of Greenstein Rogoff Olsen & Co. LLP, an accounting firm in Fremont and Palo Alto, California that caters to wealthy Silicon Valley clients.

Trump’s disclosure, which emerged during a contentious GOP debate on Thursday in Houston, Texas, was a departure from prior statements about his tax returns. He has previously suggested to interviewers that his campaign was working on preparing the returns for release and that the process was time-consuming because of their complexity.

“For many years, I’ve been audited every year,” Trump said Thursday night. “Twelve years or something like that.”

‘Strong Christian’

After the debate, Trump suggested to CNN interviewer Chris Cuomo that there might be an unsavory reason the IRS has targeted him -- because he’s a “strong Christian.”

The IRS released a statement Friday saying that “audits of tax returns are based on the information contained on the taxpayer’s return and the underlying tax law -- nothing else.”

“Politics and religion do not factor into this,” the agency said in the e-mailed statement. “The audit process is handled by career, non-partisan civil servants, and we have processes in place to safeguard the exam process.”

Federal privacy rules prohibit the agency from discussing individual tax matters, according to the statement, but “nothing prevents individuals from sharing their own tax information.”

The issue moved to the top of the agenda this week after Mitt Romney, the 2012 Republican nominee -- and no stranger to controversy over tax returns himself -- said in an interview with Fox News that Trump’s tax returns may contain a “bombshell.” Romney speculated that Trump’s personal tax documents might show that he is not as wealthy as he has claimed. On Thursday night, Romney needled Trump again, posting on Twitter: “No legit reason @realDonaldTrump can’t release returns while being audited, but if scared, release earlier returns no longer under audit.”

Trump, who has said he’s worth more than $10 billion, has responded by calling Romney a failed candidate and posting on Twitter: “Just for your info, tax returns have 0 to do w/ someone’s net worth.”

Bombshell Revelation

Olsen said that Trump’s revelation about 12 years of audits is something of a bombshell itself. “If the IRS examines your tax return and finds no issues they will not audit your return again for two years,” he said. “If returns are properly prepared, the IRS typically goes away.”

Pressure on Trump to release tax information may only build through the weekend as his two main rivals for the GOP nomination announced plans to release their own tax documents.

Senator Ted Cruz, who released some tax returns during his 2012 U.S. Senate race in Texas, said he’ll make more returns public as early as today. Senator Marco Rubio, who released some tax documents during his 2010 Senate race in Florida, said he’ll release additional information as well.

On the Democratic side, Hillary Clinton has released several years’ worth of returns, through 2014, when she and former President Bill Clinton reported adjusted gross income of $27.9 million. Senator Bernie Sanders has released part of his 2014 return, on which he and his wife, Jane, reported $205,271 in adjusted gross income.

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