AhlulBayt News Agency - Significant territory losses means the number of people living in the Jihadi caliphate slumped from nine million at the start of 2015 to fewer than six million.
It has caused the blood-thirsty groups' tax receipts to plummet from around £56million each month to £40million, according to the tax report by consultancy firm IHS.
The death-crazed cult – also called Daesh – was once even branded the "richest terrorist group" in the world.
But now desperate jihadi taxmen are reported to be imposing ridiculous fines.
Ludovico Carlino, senior analyst at IHS, said: “Our research has found that the so-called Islamic State is increasing taxes on basic services and coming up with new ways to get money from the population.
“You can be fined for driving on the wrong side of the road and for not being able to answer religious questions based on Wahhabi, Salafi beliefs.”
It is also claimed that the so-called Caliphate slapped taxes on "installing satellite dishes" and instated "exit fees" for people trying to leave a city.
ISIS receives half its revenue from taxation and confiscation while selling and smuggling oil makes up 43 per cent of its cash.
But both income streams have been smashed after ISIS’ territory shrank by nearly a quarter.
And the depraved Islamist group suffered another setback after it was revealed that a "precise" air campaign wiped out more than 25,000 jihadis.
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