Assuming you are referring to Boxes 18 and 19 of your Form W-2:
If there is a dollar amount in Box 19, Local Income Tax, TurboTax will expect there to be an amount in Box 18, Local wages, tips, etc. There should also be an entry in Box 20, Locality name. If your employer left Box 18 blank, and all of your income was earned in the same locality, then the amount from Box 1 would normally be repeated in Box 18. If you have a question as to how your Local Income Tax was determined, ask your employer or payroll office. If there is an error, they may need to issue you a corrected W-2.
See this TurboTax tips article for more information about Form W-2.
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