Log in to the GST portal using your username and password
Go to the Dashboard
Click on the profile icon or the username at the top right
Select My Profile
Open the Non-Core Fields or Amendment of Registration section
Choose the option to amend the mobile number
Enter the new mobile number
Verify the new number using the OTP sent to it
Submit the application with DSC, EVC, or E-sign
Track the status of the amendment under the Services section
Once approved, the mobile number will be updated in the GST portal