The marking pattern for the UPSC civil services prelims involves a negative marking scheme. For each incorrect answer, a deduction of one-third of the marks assigned to that question is applied. This policy discourages random guessing, prompting candidates to demonstrate their knowledge accurately. Each paper in the prelims typically consists of 200 multiple-choice questions, with a total of 400 marks available. Thus, understanding this marking pattern is crucial for aspirants when strategizing their approach to answering questions during the exam, as it directly influences their overall score.