For this, you would need to:
- Go to the official website of FASTag of your issuer bank authority or the FASTag service provider that gave you the tag.
- Go to the Contact section of the website.
- Find the customer support number in the section and speak to an executive from the issuer bank/service provider to help you with finding the required details.
- You would be required to provide your vehicle registration number to the executive.
- Once your vehicle number is verified by the executive, they would help you with the FASTag customer ID.