the issue I see with a fleet card given to your employees, is how to prevent them from using it on a trip to a nearby casino. the other problem is to the extent they pay for gas with the card and drive the vehicle for personal purposes, is that in order for the corp to get the deduction, you would have to include the personal portion on their W-2. an almost impossible accounting task
if you don't, and the IRS audited the Corp, they would probably disallow the entire amounts reimbursed.
better would be to establish a plan where the employees submit a mileage report . once a week, twice a month, whatever you want to use, they submit a written report. it would have to include where they went and mileage. note, only mileage from your place of business to job and back would be business and be reimburseable and still not taxable. you would use the federal reimbursement rate 58 cents per mile.
you have the same problem. using a company credit card to pay for gas used for personal purposes. personal portion probably taxable compensation. so yes you can pay for 100% of your gas with company credit card but keep written records to support business portion. the nonbusiness portion would probably be consider compensation that would have to be added to your W-2. the standard mileage rate includes fuel, so deducting fuel cost on S-corp and taking the standard mileage deduction on 1040 would be frowned upon by the IRS. I assuming your taking the standard mileage deduction to schedule E to offset S Corp because employee business deductions on schedule A have been eliminated for 2018-2025.
