Looking at Braintree's Marketplace docs, it appears you have to "onboard" each sub-merchant you want to send payouts to, which requires entering their name, address, date of birth, and their social security number. It then says "If [the social security number] is not provided, we will attempt to retrieve the full Social Security number based on the other applicant details."

So my question is: How is it possible / how do they retrieve someone's social security number using apparently just a name, address, and birth date? (Maybe I'm naive, but I thought socials were pretty secure)