How can I estimate the registration fee and tax for boats and trailers?
They are calculated differently. You can use the online service to estimate them
Regarding proof of payment of sales tax, if I bought the vehicle when I was not a resident of New York, what should I do?
In that case, use the New York State Department of Tax and Finance DTF-803 Sales Tax Exemption Form {Sales Tax Form} pdf to receive a - New York State Resident Exemption. Form DTF-803 defines the terms "non-resident" and "resident".