Donald Trump's 12-year audit? It's pretty fishy, a former IRS agent says.

Donald Trump has chronically dragged his feet on disclosing his tax returns, claiming that the process of preparing the returns was time-consuming, and then flipping his story to say he was being audited by the IRS. Despite the fact that being audited in no way prevents someone from releasing returns, there was perhaps a major revelation in Trump's excuse — "For many years, I've been audited every year, 12 years or something like that," Trump said during Thursday night's Republican debate.

Former IRS agent Alan Olsen said to be audited every year for the past 12 years is a "very unusual" level of scrutiny, Bloomberg reports. "He signed his name to a return in which the IRS is finding problems for the past 12 years," Olsen said.

While Mitt Romney has said that Trump's tax returns may hold a "bombshell" revelation, such as Trump not being worth the $10 billion he claims, Olsen said the 12-year audit was news in and of itself. "If the IRS examines your tax returns and finds no issues they will not audit your return again for two years. If returns are properly prepared, the IRS typically goes away," Olsen said.

Trump has countered such statements by saying the IRS is paying particular attention to him because he is a "strong Christian."

Sen. Ted Cruz, Sen. Marco Rubio, Hillary Clinton, and Sen. Bernie Sanders have all released returns, with some of the candidates promising even more information is on the way.