A leaked document which appeared online on Football Leaks on Wednesday claims that City paid much more for the 24-year-old than the £32million they initially indicated.
When City purchased the French defender from Porto in the summer of 2014, the Portuguese club owned just 56.67% of his economic rights with the remainder being split between The Doyen Sports Investment Limited (33.33%) and an Austrian marketing company (10%).
It is believed that City had to pay £24m to buyout Porto's share which took the deal to £41.4m.
Mangala has shown glimpses of his enormous potential since his arrival at the Etihad Stadium but supporters will be shocked to learn how much the club have shelled out for his services.
The Manchester Evening News suggests that City have not commented on the leaked document which shows they have paid a lot more than was originally claimed.