The recommended age limit for candidates appearing for the UPSC exam varies by category; generally, candidates must be between 21 and 32 years at the time of applying. There are relaxations: OBC candidates get a three-year extension, while SC/ST candidates receive a five-year extension. Additionally, candidates with disabilities can avail of longer age limits, depending on their category. It's essential for applicants to verify their eligibility and ensure they meet the necessary conditions as per the official UPSC guidelines to avoid any last-minute disqualifications.