As you want to become IRS Officer so here I am giving you details including Selection Procedure and Eligibility Criteria.

Eligibility Criteria:

Educational Qualification:
Candidate must possess a degree from an Indian University or an equivalent qualification. Candidate of final year of a degree course can also appear in the Preliminary Examination taken every year by UPSC.

Age Limit:
Candidate must have attained the age of 21 years on 1st August of the year of examination and must not have attained 30 years of age on that date.

Upper age limit will be relaxed by 3 years for OBC candidates and 5 years for SC/ST candidates.

Nationality:
a citizen of India, or
a subject of Nepal, or
a subject of Bhutan, or
a Tibetan refugee who came over to India before January 1, 1962, with the intention of permanently settling in India, or
a person of Indian origin who has migrated from Pakistan, Burma, Sri Lanka, East African countries of Kenya, Uganda, the United Republic of Tanzania, Zambia, Malawi, Zaire, Ethiopia and Vietnam with the intention of permanently settling in India.
How to become an IRS officer?

Selection Procedure:
Preliminary Exam
Final Exam
Interview

Exam Pattern:

Preliminary Exam:
1. General Studies: 150 marks
2. Optional Paper: 300 marks

Optional subjects –
1. Agriculture
2. Animal Husbandry and veterinary science
3. Botany
4. Chemistry
5. Civil Engineering
6. Commerce
7.Economics
8. Electrical Engineering
9 Geography
10. Geology
11.Indian History
12.Law
13. Mathematics
14.Mechanical Engineering
15. Philosophy
16. Physics
17. Political Science
18. Psychology
19. Public Administration
20. Sociology
21. Statistics
22. Zoology

Final exam:
1. 1 Essay type Indian Language Qualifying Paper: 300 marks
2. 1 English Qualifying Paper : 300 marks
3. 1 General Essay type paper : 200 marks
4. 2 General Studies papers: 300 marks each
5. 4 Optional subjects papers: 300 marks each