The following steps will guide you apply for the mentioned certificate through online.
1) Open http://www.gad.bih.nic.in/ website.

2) Look into right sidebar “Latest updates …”. You can see “News: Apply Online for Caste, Income or Residence Certificates. – 01-12-2011″ link which scrolling there, click that web link.

3) Once you visit that page it will take you to http://210.212.23.51/aa/ this web page.

4) Read the given instruction and rules carefully and click on “I Agree” link to proceed further.

5) The initial screen will ask you the details like Name, Certificate, and mobile number. You have to choose any one of certificate from the list Issuance of Income Certificate ( CO ) or Issuance of Residential Certificate ( CO ) or Issuance of Caste Certificate ( CO) . Once you entered the required details press on Next button to fill all the required details carefully and complete the online registration.

For more Information visit,
http://www.gad.bih.nic.in/