No, your personal data and personal transactions unrelated to the e-submission on CORENET 2.0 will not be shared with IRAS or other related agencies. Your Singpass is only used as a secure login and user authentication mechanism to verify the identity of individual users before accessing CORENET 2.0 services.
If any of your personal information is required by a related agency/organization, you will be prompted with a consent screen and you will need to give your consent to retrieve Myinfo from your Singpass account before any personal data can be shared.