A charity once led by U.S. Senate candidate Roy Moore has put its historic building in Montgomery, Ala., up for sale, a transaction that could bring Moore $540,000 because of an unusual compensation arrangement he made while serving as the nonprofit group's president.

The 1850s-era building was put on the market in April for nearly $1.9 million by Moore's wife, Kayla, now president of the charity, said Ed Fleming, the listing agent for the property. Fleming said Kayla Moore and her husband were "thinking of moving and retiring" at the time.

"I deal with Kayla. She made the decision," he said.

The circumstances of the listing add to questions swirling around the charity and more than $1 million in compensation for Roy Moore while he was working part time from 2007 to 2012. Kayla Moore took over as president in 2013, earning $65,000 a year.

 On Wednesday, The Washington Post revealed that the nonprofit group, the Foundation for Moral Law, agreed to pay Moore $180,000 in annual salary, far more than the charity reported paying him in most of those years, and to honor the agreement even in years it did not have enough in contributions.

Moore was given a promissory note for back pay in 2011, tax filings and mortgage documents show, the first public indication that his annual compensation surpassed what had been reported. The note, backed by a second mortgage on the building that serves as the charity's headquarters, was eventually worth $540,000, mortgage records show.

Kayla and Roy Moore declined multiple requests for interviews.

Brett Doster, a campaign spokesman, defended the couple and the decision to put the building up for sale. "The Foundation is governed by a board, not an individual staffer," Doster said.

"Judge Roy Moore is an honorable man who has performed his service to this country according to the highest of ethical standards," he said in a statement. "We disagree with the assertions and conclusions of your previous story and see no reason to continue the conversation."

It is unclear whether the board authorized the sale of the building or whether Kayla Moore acted on her own. Doster did not respond to a question about whether the board had authorized the sale.

Board member John Bentley, a circuit court judge in Alabama and a former chairman of the board, said that he did not learn of the listing until Thursday afternoon, from a reporter. Bentley told The Post he confirmed the listing during a call with Rich Hobson, Moore's campaign manager and a former executive at the charity.

"I'm a board member, and the first I heard the building was on sale was today," Bentley said, although he acknowledged missing the two most recent annual board meetings for personal reasons.

The charity was founded during Moore's legal battle over his decision to install a granite Ten Commandments monument in the state Supreme Court building. Moore joined it after he was ousted from the court for refusing to remove the monument. The charity bought the building in 2005 for $546,000 and spent hundreds of thousands more to renovate it.

As of January 2014 the charity had a $500,000 first mortgage on the property.

Built in 1856, the Renaissance Revival building has an iron exterior and several offices, including one with law books and a portrait of Moore, according to a promotional video online. Tours are by appointment only.

"It's strictly a premier piece of property," Fleming said.

In its report Wednesday, The Post found that errors and gaps in the charity's tax filings and internal documents obscured the compensation paid to Moore, who last month became the GOP nominee and front-runner to fill the seat vacated by Attorney General Jeff Sessions.

The charity has filed scores of legal briefs in cases involving conservative Christian issues. It also has helped Moore maintain his national profile by promoting his speaking events.