I'm pretty sure you can apply for a rebate of the FEDERAL ROAD tax as well. Farmers do this as a matter of course in their business; it goes back to when the tax was started. They wrote the wording of the tax so that only gas used on government roads was taxed ... farmers were the main business back then and made sure they were taxing everyone else back then and not themselves.
You don't have to use the boat as a business to ask for rebate of the ROAD TAX if you can prove you used the gas
off-road.
Here's my prediction for the future of taxes in the high tax states: taxes on most services ... except for banking services ... guess who is making the rules these days?
