In the order to become Income Tax Officer, you need to appear in the CGL (Combined Graduation Level) Examination which is conducted by SSC (Staff Selection Commission) in Yearly ones. Here I am giving you the details of this examination:

Eligibility:
The applicant should have completed graduation with good academic record from any recognized university of India.

Age:
Age between 18 to 28 years, age relaxation as per norms, as under
For SC/ST 5 years
For OBC 3 Years

Physical Standards (Minimum)
Height :157.5cm
Chest :81cm ,fully expanded with a minimum expansion of 5 cm
Physical Test:
Walking:1600 meters in 15 minutes
Cycling:8 Km in 30 minutes

The entrance examination will cover following topics:

General Intelligence
General English
Arithmetical Ability
General Awareness