On form 1040, schedule C-EZ,should I have written evidence to support my vehicle expenses and miles driven? Do I risk being audited if no is checked for evidence?

Yes, you should have written evidence of the mileage that you are deducting. Under IRS listed property rules, the IRS can disallow any and all vehicle expenses if there is no mileage log.

Yes, there may be a bit of an increase is your audit risk if the evidence box is checked no. This is stating to the IRS that you do not have a key record to sustain your vehicle expenses if they were to audit your return.