A question that comes up frequently from people with home-based businesses is if they can deduct mileage driven from their home to a work site. The answer can be tricky. IRS publications say that you can deduct mileage driven from your home to work sites if your home is your principal place of business. But it’s actually more complicated than that: to qualify as a principal place of business, your home office must be used regularly and exclusively as your principal place of business. The “exclusive” part of the requirement is what sinks most people.
It should be noted that the regular and exclusive requirement is the same requirement for claiming the “business use of home” deduction. This raises another question: must you claim a deduction for business use of the home in order to claim a mileage deduction for mileage driven from the home office to a work site? The answer is no; you can claim the mileage deduction without claiming the business use of the home deduction — but in order to meet the requirements to deduct mileage, you have to meet the requirements for claiming the business use of home deduction.
Assuming you are home-based but that your home office is not used exclusively for business purposes, mileage driven from your home office to your first business stop would not be deductible, but mileage between other business stops is deductible. So with a little planning, you can still deduct at least some of your mileage. For example, drive from your home to the post office to check your business PO box (mileage not deductible). Then drive from the post office to another business stop (mileage is deductible). Mileage driven from business stop to business stop is deductible, but the mileage from your home to your first stop, or from your last stop back to your home, would not be deductible.
It’s different if your home office qualifies as your principal place of business under the regular and exclusive tests. Then, any business miles you drive from or to your home office are deductible.
A recent Tax Court case went into more detail about this issue.