You won't see a special place to enter the vehicle excise tax deduction on your Massachusetts state return, either in the TurboTax software or elsewhere, because it simply does not exist. The vehicle excise tax deduction is a federal item, and is specifically reported to the IRS on Form 1040, Schedule A, Line 7 (please see the attached image at the bottom of this answer for a visual reference).
Your Massachusetts tax return already incorporates the federal Schedule A amounts into its calculations automatically, as the tax return begins -- so if you attempted to enter the state vehicle excess tax a second time (by mistake), you would effectively be getting a double-deduction for the same item, on your state taxes, since the deduction is already included (by default) in your Massachusetts return.
That's the short answer to your question. For a more detailed discussion of this topic, you may wish to continue reading.
The amount eligible for the vehicle registration fee deduction, for
Massachusetts registered vehicles, is simply the excise tax itself, not
the whole amount of the cost of registration.
The legal reasoning is as follows. The IRS only allows that portion of a state registration fee that is based on the value
of the vehicle to be included toward your other itemized deductions.
Any flat fee portion doesn't count. This is why there are some 20+
states whose residents can potentially benefit from the deduction
(including MA), but the remainder cannot: their states do not charge
vehicle registration fees by value, and instead charge flat fees only.
You can read more about the MA excise tax and how it is calculated here, if you are curious:
http://www.mass.gov/dor/local-officials/municipal-finance-law/frequently-asked-questions-motor-vehic...
Now then, it is also important to keep in mind that you (or
anyone claiming this deduction) may or may not actually see any net tax
benefit from including this item on your tax return. The reason for
this is that you must have enough itemized deductions (in total) to
exceed the standard deduction available to all taxpayers. Since more
than 2 in 3 taxpayers do not, most people end up taking the (more
valuable) standard deduction, rather than itemizing deductions. If you
input all your data carefully, including the MA vehicle excise tax,
however, the TurboTax software will make that determination for you.
Thank you for asking your question, and hopefully you will find this information helpful.
