The basic eligibility criteria for the UPSC Civil Services Exam include being a citizen of India, possessing a bachelor's degree from a recognized university, and meeting age limits, which vary with categories. General category candidates typically have a maximum age limit of 32 years, while there are relaxations for candidates from reserved categories. Additionally, candidates must ensure they fulfill the stipulated number of attempts permitted for each category. Thoroughly understanding the eligibility criteria is essential for aspirants to ensure they meet the requirements before applying for the examination.