Evidence of the group’s failing financial state has been mounting as it cut fighters’ salaries in half for a second time earlier this year.
The U.S. military has said ISIS has lost control of roughly 40 percent of its territory, though eight million men, women and children still reside in occupied lands.
Those who remain face an array of taxes, all marketed as zakat, or tithings. There is a 10 percent income tax, up to 15 percent in business taxes, five percent fees for cash withdrawals and up to 35 percent in taxes on essential drugs.
Christians must also pay the jizyah tax, which ensures their protection from ISIS’ enforcers.
“It’s really an adaptive organization,” Brisard told CNNMoney. “What strikes me is the fact that they’re clearly behaving as managers, not simple looters. They really have budget requirements, and they’re compensating.”