I use my car for my business. I traded my old car for a new 2017 in 2017. I paid a down payment and paid sales tax on vehicle. Can I file these two expenses?

Yes, you may take two cars off for your business, as long as you used both for business.

You can either take actual expenses, which include sales tax paid, or you can take standard mileage (53.5 cents in 2017). 

Actual expenses include

• gas
• oil
• insurance
• repairs
• depreciation

Sales tax paid is added to the basis of your car when you set it up for depreciation.

Keep in mind that one you start taking car expenses using the actual method, you're stuck with that method; you can't switch to taking standard mileage. 

Will a bank statement work in place of gas receipt?

Yes, as long as it's documented you can.