Do you have other kinds of proof?
No, I do not need to bring other proof I have the completed Vehicle Registration.
What proof of payment do I need to show for the sales tax paid?
You would need an FS-6 T receipt issued by the DMV, or obtain a Claim for Sales Tax Exemption from the leasing company and a bill of sale; or a Dealer Retail Certificate of sale MV-50 completed by the dealer located in New York state.