The final merit list for UPSC candidates is prepared based on the combined scores from the Preliminary examination, the Main examination, and the subsequent Interview or personality test. Candidates must first clear the Preliminary exam to qualify for the Main exam. The scores from all phases are then normalized to create a comprehensive ranking. This method ensures that the final list reflects a candidate's overall performance across all evaluation stages, aligning with the UPSC's goal of selecting the most competent individuals for civil services.