Can you explain more of what you mean?
The instructions for the sales tax deduction are that you can deduct taxes if you pay the "general sales tax rate." I don't know Texas, but I used to live in New York, and New York State charges 4%, and local counties can add on top of that, so Monroe County was 8.25% and Ontario county was 8%, for example. Because you can only deduct sales tax paid at the general rate, you couldn't deduct the taxes on liquor or gasoline (which were separate taxes from general sales tax).
There are special rules for food and automobiles. You can deduct the actual tax you paid if it is less than the general sales tax rate, but if the tax rate is more than the general sales tax rate, you can only deduct up to the general sales tax rate for those items. (For example, where I now live in Virginia, the general sales tax rate is 6.5%. Restaurants in the city limits have a 11% restaurant tax, some grocery items are tax-free and some grocery items have a 1% sales tax. I could deduct 6.5% for in-city restaurant meals, 1% for taxed grocery items, and nothing for non-taxed grocery items.)
With that baseline, what is your actual question. Are you trying to use the actual method (where you add up all your receipts and deduct what you actually paid) or are you using the optional standard method (where the IRS assigns a deduction based on your estimated spending based on your income and where you live)?
And if you are using the optional standard method, and you want to add the tax paid on the purchase of a car, what problem are you seeing?
