You can login to your account with Mobile number and OTP but in Go GST Bill you also have option to login with Userid and password. This method is useful when you do not want to wait for OTP or if your phone is not with you, or in case you lost your phone.
To create your Userid and Password please follow the steps below.
Step 1: Click on profile icon and than click on Settings option
Step 2: Click on Login & Security under Settings
Step 3: Under User Details section Enter User ID, Password, Confirm Password & Verify with OTP.