The purpose of this thesis is to investigate the plaintiffs and the defendant’s prospects to change their claims and pleas in optional civil actions and how the rules for the modifications of a suit are affecting the framework of the process. The plaintiff's general ability to expand and alter the claim is found in the chapter 13, 3 § of the Act of Procedure and the basic principle is that a claim is not to be changed. From this basic principle exceptions are allowed to claim another fulfillment or to expand the process with a claim for interest or other additional obligations. The plaintiff can also limit his or her claim or expand the claim with new legal foundations as long as the issue of the process does not change. The defendant’s prospects to make changes in his or her plea are limited to admission and setting off.