new work van purchased

If you are a W-2 employee then be aware that W-2 work related expenses are no longer deductible. Not a penny.

If you are self-employed, you deal with business vehicle use in the SCH C section of the program under the section clearly titled "Business Vehicle Use".

Note that what you paid for the vehicle is *NEVER* deductible. Not a penny. It gets depreciated. How it's depreciated depends on if you take the actual expense option or the per-mile option. But under no circumstances can you "DEDUCT" what you paid for the vehicle. That includes the down payment. But you can claim as a business expense any interest you pay on the loan.

Overall you'll most likely find the "per-mile deduction" method to be significantly better than the actual expenses method. But whichever method you chose in that first year, you will need to keep finely detailed records to prove everything if ever audited. If you can't prove it in writing, then the claim will be disallowed. You can count on it.

if you are an employee, you need to read no further.   

what do you mean deposit?   did you take delivery?

if so why would you want to deduct only the deposit and not the full cost of the vehicle?   

we know nothing about it,  so what you can deduct may be limited.  

what type of vehicle auto, Suv, pick-up, cab, hearse, limo,  over-the-road tractor-trailer.  what % business use?