The minimum age requirement to appear for the UPSC Civil Services Examination is 21 years on 1st August of the examination year. Candidates must also be unmarried or legally married, and must not exceed the upper age limit, which varies by category. For instance, those in the General category have a maximum age of 32 years, while OBC candidates have a limit of 35 years, and SC/ST candidates can apply until 37 years. There are various allowances for candidates with disabilities and other special categories.