Where do I put my business logic in mvc?

Controller action takes the request , process it and returns the required results in action result . The purpose o controller is not to handle any business logic . The purpose of mvc is separation of controller model view . Controller process the request , model is a place holder of data , contain the business logic , view contain the UI look and fill. For putting the business logic you can have a repository or business layer code which will process the data and assign it to the model . If you place business logic in controller it will be difficult to maintain, difficult to unit test the controller code .