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Car expense deductions with multiple work locations
Suppose that I work from home, but do not qualify for a business use   of home deduction. As I understand it, this means I cannot deduct   trips from home to another work location (e.g., going to a client's   home or office to do work there). I do not think this is true. You cannot deduct trips to your main business location, i.e.: you cannot deduct trips to your office or client's location if this is your main client and you routinely work on-site. However, if you only visit your clients on occasion for specific events while doing your routine work at home - you can definitely deduct those trips. The deduction of the home usage itself has nothing to do with it. However, there's a different reason they refer to pub 587. Your home must qualify as principal place of business (even if it doesn't qualify for deduction). The qualifications of "principal place of business" are described in pub 587. "if for some personal reason you do not go directly from one location to the other, you cannot deduct more than the amount it would have cost you to go directly from the first location to the second." What is not clear to me is what exactly is deductible if there are   significant time gaps (within a single day) between trips to different   clients. You got it right. What this quote means is that if you have client A and client B, and you drive from A to B - you can only deduct the travel between A and B, nothing else. I.e.: if you have 2 hours to kill and you take a trip to the mall - you cannot deduct the mileage attributable to that trip. You only deduct the actual distance between A and B as it would be had you driven from A to B directly. The example you cite re first client being considered as the place of business is for the case where your home doesn't qualify as principal place of business. In this case you start counting miles from your first client, and only for direct trips from client to client. If you only have 1 client in that day, tough luck, nothing to deduct. Also, it's not clear whether stopoffs between clients would really be   "personal reasons", since the appointment times are often set by the   client, so it's not as if the delay between A and B was just because I   felt like it; there was never the option of going directly from A to   B. That's what is called "facts and circumstances". You can argue that you had enough time between meetings to go back to your home office to continue working. The IRS agent auditing you (and you're likely to get audited) will consider that. Maybe will accept it. Maybe not. If I had a gap like that described above, I could save on my taxes by   going to the park or a hamburger stand instead of going home between A   and B But then you wouldn't be at home, so why would it be "principal place of business" if you're not there? Boom, lost deduction for the trip to the first client. I suggest you talk to a licensed tax adviser (EA/CPA licensed in your State). You're dealing with deductions that are considered "red flags" for the IRS. I.e.: many people believe that these deductions (business use of your home/car) trigger audits. To substantiate business use of your car you need to keep very good track of your travels (literally travel log, they sell them at Staples), and make sure to distinguish between personal travel and business travel, keep proofs that the meetings took place (although keeping a log is a requirement, it can be backdated/faked, so if audited - the IRS will want to see more than your own documentation). A good tax adviser will educate you on all these rules, and also clarify the complexities you were asking about here. I'm not a tax adviser, so don't rely on this answer when you're preparing your tax return or responding to the IRS audit. In your edit you ask this: Specifically, what I'm wondering is whether it is possible for a home   to qualify as a "principal place of business" for purposes of   deducting car expenses but not for the home office deduction. The answer is yes. Deductibility is determined by exclusivity of use, among other things. But the fact that you manage your business from your kitchen doesn't make your kitchen any less of a principal place of business. It is non-deductible because you also cook your dinners there, but it is still, nonetheless, your principal place of business. The Pub 587 which I linked to has these qualifications: Your home office will qualify as your principal place of business if   you meet the following requirements. You use it exclusively and regularly for administrative or management activities of your trade or business. You have no other fixed location where you conduct substantial administrative or management activities of your trade or business. As you see, exclusivity of the usage of your home area is not a requirement here. The "exclusively and regularly" in the quote refers to your business not using any other location, and managing it from home regularly. I.e.: if you manage your business a day in a year - that's not enough for it to be considered principal. If you manage your business from your office and your home - you cannot consider home as principal.