It is always advisable that student must keep login credential like registration number and password safe for future. If you have forgot your Kar tet registration number no need to worry as most of examinations conducting authority send registration number details via sms and email. You can check your sms and e-mail you will get your registration number.
If you cannot find it there you can raise your issue by writing a mail to authority
Kar TET Helpline Phone Number:080-22228805, 22271866, 22483145
Kar TET Help Desk Toll Free Number:
Kar TET Fax No:+91-080-22212137.
Kar TET Helpline Email Id:email@example.com
Hope this will help
Best of luck.