My W-2 has two lines of data for box 18-20 but turbo tax says I should only have 1. Where or how should enter the 2nd set of data? Both lines are labelled, LOCAL T.

[RaifH]

To add the second set of local taxes, you may click on the Add another locality button underneath Local Taxes on your W-2 information.

Some states changed the rules on which locality got to collect the taxes, especially for telecommuters during the pandemic. It is also possible you got taxed on your wages both by your resident locality and your employer's locality. You do get a federal deduction for local taxes paid during the year. 

Local tax returns cannot be efiled through TurboTax. Filing may or may not be necessary, depending on your locality.