What state are you in? What exactly is in box 20? You're expected to know what locality is withholding tax from your pay. If not, ask your employer. It's usually the city/county you work in. But can sometimes be different.
In most situations, it's not very relevant; they took it out of your pay and that's the end of it. But, in others, you may have to file a local tax return and may even be subject to a refund (unusual).
If you itemize deductions, on your federal return, the box 19 amount is deductible. TurboTax will usually pick that up automatically, regardless of the gobbledygook in box 20.
