To figure the amount of optional general sales tax you are eligible to claim, just answer a few online questions and the system does the rest. First select the tax year for which you are preparing a return. Then, using your ZIP Code and just a few entries from your draft Form 1040, the Sales Tax Deduction Calculator will automatically figure the amount of state and local sales tax you can claim. You will see the results from your entries immediately on your computer screen. Even if your state and local sales tax rates changed during the year (e.g., because the rates changed or because you moved your personal residence), the Sales Tax Deduction Calculator can handle it.