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How to buy out one person's share of a jointly owned vehicle with the lowest taxes and fees
You should be able to refinance the vehicle and have the financing in just your name (assuming you can secure the financing). Since you are already on the vehicle registration, this would not constitute a sale, and thus would not incur additional sales tax.  To remove the other person from the vehicle registration, leaving you as the sole registered owner, in the state of New York, you only need to file an MV-82. It will cost you $3. https://dmv.ny.gov/registration/register-vehicle-more-one-owner-or-registrant