The Islamic State has introduced fines for not knowing the Quran well enough, among other financial penalties. The cash strapped group is thought to have lost some 30% of its income stream over the past year.
Other penalties include duties for installing satellite dishes, tolls for truck drivers and exit permits to leave cities.
ISIS was making $80 million per month in mid-2015 and is making only $56 million per month today, according to the American analysis firm IHS. The group has lost 22% of its territory over the past two years and seen its subject population decrease from nine million to six million.
As a result of U.S. and coalition air strikes, ISIS oil production has dropped from 33,000 to 21,000 barrels a day.
“Islamic State is still a force in the region, but this drop in revenue is a significant figure and will increase the challenge for the group to run its territory in the long term” IHS senior analyst Ludovico Carlino told media.