TIN stands for Tax Identification Number. That’s either your Social Security Number (SSN) or Employer Identification Number (EIN), depending on how you filled out your W9 form in your AdThrive dashboard.
You can check to see which you used by logging in to your dashboard, clicking on Payments in the left sidebar, then selecting "Payment Info" from the dropdown menu.
Click through to page three: Tax Forms, and click where it says "To view the information you submitted, click here."
Under "W9 Form Details", it will list which tax identification number you entered on the W9 form.