Hi there, @Justin1612.
As our Shipping and Payments team has already alerted you - this is coming from Stripe, our payment processor. As you know, we use Stripe to process our payments, and when Stripe can't verify the identity between user and account, they typically require more information. I'd recommend reaching out to Stripe if you're concerned because it is Stripe asking you for your social and not OfferUp.
Hey there, @Kenney! From what I've heard from our payments team, the SSN is only required at times where there may be a difference in name between the bank account and the information provided. Definitely reach out to our Payments team if you haven't already done so, and they should be able to give further information.