Visit the official transport department or RTO portal of your state
Log in using your vehicle registration details or registered account
Select the option for RC details update or mobile number change
Enter the new mobile number
Verify the number using the OTP sent to the new mobile number
Submit the request online if the portal allows it
If online update is not available, visit the nearest RTO office
Fill out the RC correction or update application form
Attach required documents such as RC copy, ID proof, and address proof if asked
Submit the form and pay the applicable fee if required
Collect the acknowledgment receipt or application number
Check the updated RC details online or through SMS after processing