There is lots of good info here, but also some that is inaccurate or misleading. I was once an attorney and did quite a bit of tax work, both as an attorney and in an accountant's office during law school years ago, but I am not in practice now and I'm not your attorney, so don't rely on what I say here. Also, each person's individual situation is different, so it's impossible to say what's right in an individual case based on a few posts here.
First as to TurboTax, I use it and I think it's great. It is not perfect, however, and I have had to file amended returns on a couple of occasions because of its mistakes or poorly worded instructions. I once use Tax Cut, the software from H&R Block, and it was horrible for a number of reasons. As to the company's guarantee/warranty of accuracy, don't count on it. They only guarantee the accuracy of the calculations, not their interpretation of the law. Basically they guarantee that if you enter income as $77,500 and a credit of $7,500, they'll do the subtraction right and get the result $70,000. That's all. They don't guarantee you're entitled to the credit and won't represent you if the IRS challenges it. I think software products are all the same on that. However, I have found that CPA's are way too expensive and not reliably better. There have been several threads on this forum where an accountant or other tax professional got things wrong.
Second, you are almost always better off taking any credit or deduction if you have any lawful non-fraudulent basis for it. The IRS rarely challenges them based on suspicion, but will normally catch mistakes that violate the mathematical rules, e.g. you are claiming a credit of more than your total tax liability. In that case, just pay the difference. The 3% interest charge (if that's the current rate), if you get hit with it, will be a lot less than the cost of a CPA or attorney. Personally, I have no fear of an audit or going to court over something like this because I'm retired and have litigating experience, but I realize that's not practical for most people. It's actually easier than people think to go to court and fight your case. If you're in the right, the judge will get it right eventually, but you can almost always negotiate a settlement on very favorable terms because the government doesn't want to litigate small cases for several reasons: the cost to them, but more importantly, the damage that would be done from the precedent if the court holds their interpretation of the tax code is wrong.
Third, if I read the document right, business use does not prevent claiming the $7,500 credit, it only means that when you sell the call, your basis is small due to the credit and the credit is in effect partially recovered by the government. Form 8936 has a business use section and I think the main purpose it to prevent you from claiming the credit for the cost of buying the car and also deduct the cost of operating and depreciating it for business use, so your credit may be reduced by the amount of business use you claim or vice versa. However, I have not researched this and only glanced at that part, so maybe I have that wrong.
Fourth, someone asked how to fight a mistaken interpretation by the auditor on this. As I think the posts show, just being civil and politely disagreeing with him or her usually gets the right result. They are honest folks trying to follow the law in my experience. Give them time to research it and by all means give them any reference materials you have on this. Even if you don't agree on the credit, you can probably work out a compromise, especially if you can find some other items where you might be entitled to a bigger refund (or less tax) that you did not claim or which are in dispute, such as mileage for volunteer work or getting to medical appointments that you could have claimed on Schedule B but didn't bother with. If at the end of their process you still want to fight it, your options are generally threefold: appeal to the Tax Court, sue the government in the Court of Claims, or sue the government in U.S. District Court. For Tax Court you do not have to pay the tax first, but for the other two you have to pay the tax first and then sue to get it back. The Tax Court has the most expertise, so that's where you want to go if you are right on the law, but it may be inconvenient to get to depending on where you live and especially expensive if you have to hire someone locally to travel there. This is true for the Court of Claims, too. U.S. District Court will generally be closer and easier, but the judges know little tax law and the process is slower and clunkier. Bankruptcy is another option for a few people, but I don't recommend that or any court action over an amount this small unless you're like me -- experienced in this stuff and have the time away from work to take it on.
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