Proof of SSN
According to the official county documentation, you can bring one of the following:
Social Security Card
W-2 Form
SSA-1099
Non-SSA-1099
Pay Stub containing individuals name and Social Security number
However, (according to user reports) if you have none of the above but do have your SSN memorized, there is an in-office form you can fill out and sign to waive this requirement. If you have any questions about this, you can always call the tax collector's office to confirm (contact info here).