In order to sell tickets on SeatGeek, you will need to provide your bank account details, and some additional information required for tax purposes. Additional info for tax purposes may include your name, address, and Social Security Number or EIN (SSN or EIN may be needed for USA sellers as per the IRS. See here for more details). In some cases, you may receive an email requesting additional information, but only if absolutely necessary to securely verify your identity.
We take your security very seriously. For more details on why certain info may be required, please check out this article.