Informal Cases, unlike Formal Cases, are marriage cases that can usually be handled without extensive testimony from witnesses. This does not mean there is no work by the Petitioner, but the process is not as extensive as the Formal Case. There are two types of Informal Cases.
Documentary Cases are cases that can be shown by documentary evidence that the previous union was not valid.
Privilege Cases are cases that can be resolved by utilizing a "privilege" allowed by Church Law.