Line 5. The deduction for state and local taxes is generally limited to $10,000 ($5,000 if married filing separately). State and local taxes subject to this limit are the taxes that you include on lines 5a, 5b, and 5c. Safe harbor for certain charitable contributions made in exchange for a state or local tax credit.
A taxpayer makes the election by checking box 5a on Schedule A of Form 1040. If you elect to deduct state and local general sales taxes, you can use either your actual expenses or the optional sales tax tables.
Itemizing requirements In order to claim itemized deductions, you must file your income taxes using Form 1040 and list your itemized deductions on Schedule A: Enter your expenses on the appropriate lines of Schedule A. Add them up. Copy the total amount to the second page of your Form 1040.