Donald Trump’s former campaign manager, Paul Manafort, is currently under multiple investigations by the FBI, the Treasury, and the House and Senate select committees on intelligence for his various “Russian entanglements.” But his New York City real estate transactions have also been garnering intense interest lately—namely because some strange patterns have emerged regarding three properties he owns throughout the city, raising suspicions of (as yet unproven) money laundering.

Now, one of those properties—Manafort’s 43rd-floor condo at Trump Tower, which he purchased for $3.6 million in 2006—is at the center of another investigation, this time involving an illegal property tax break. According to the New York Daily News, Manafort has been receiving as much as $5,000 per year as part of a tax abatement program available to NYC condo owners. Per the city’s Department of Finance, the abatement is available only if a property is used as the owner’s primary residence—and that’s where it gets problematic with Manafort.

According to the Daily News, Manafort has claimed both the Trump Tower condo and a condo in Palm Beach, FL as his primary residence; he’s registered to vote based on the Florida address, and even voted in that state in the 2016 election. And crucially, Manafort has also received a tax break on that condo under a program known as the Homestead Exemption—which is, of course, not allowed if his primary residence is elsewhere.

For his part, Manafort claims that he wasn’t aware that he was still receiving the tax break on the Trump Tower property, since he considers Florida to be his primary residence. “He has not asked to change his residence to New York State. … We are reviewing the matter and will, if necessary, make any correction,” Manafort’s lawyer, Bruce Baldinger, told the Daily News.

The double-tax issue highlights a larger problem with how New York’s DOF implements these abatements. Per the Daily News, “the agency doesn’t make property owners certify in writing what they claim as their primary residence”—making it easy for issues like this, intentional or not, to slip between the cracks.

“This raises serious questions and concerns,” comptroller Scott Stringer, who’s argued for more stringent oversight of the city’s property tax abatements, told the paper. “No matter how powerful someone may be, everyone has to play by the same rules.”