If they aren't (currently or not) reporting to the IRS, why are they requiring SSN?
I was wondering the same thing
AML/KYC regulations. The issue isn't taxation, but money transmission. Chairman of the SEC, Jay Clayton,
made that clear in a statement last month:
As I have stated previously, these market participants should treat payments and other transactions made in cryptocurrency as if cash were being handed from one party to the other.
US money transmiters fall under the jurisdiction of the
Bank Secrecy Act, which requires KYC. The exact requirements (for example, whether SSN is
really required) aren't clear to me. But it seems like Bitcoin exchanges are increasingly seen as "financial institutions":
The BSA requires financial institutions to engage in customer due diligence, or KYC, which is sometimes known in the parlance as know your customer. This includes obtaining satisfactory identification to give assurance that the account is in the customer's true name, and having an understanding of the expected nature and source of the money that flows through the customer's accounts.