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.”