Q. Does the IRS have a number of miles that is considered a Average Daily Commute, i.e. 25 miles each way?
A. No. Your employer is to impute the value of your personal use, of the company vehicle, based on actual mileage.
Q. Does it apply to both Company Cars and Personal vehicles used for company purposes?
A. No. As the other answer indicated; if your company pays a W-2 employee an allowance (as opposed to mileage reimbursement under an "accountable plan") for the business use of your personal car, you get no deduction and the entire allowance is taxable to you.
Q. If a sales person works out of their Home Office, and uses a company car, are they docked mileage for a daily commute, i.e. 25 miles each way, to visit customers if they leave and return on the same day?
A. No, as far as the IRS is concerned (see reference). But, that doesn't prevent your employer from having such a policy.
Q. What if they leave for the week, i.e. leave on Monday, return on Thursday, seeing customers all week. Are they to deduct an average daily commute, i.e. 25 miles, for the outbound and return?
A. Same answer applies
Reference: https://www.bdo.com/insights/tax/compensation-benefits/taxation-of-employees%E2%80%99-personal-use-o...
