Why is TurboTax choosing state/local income tax deduction (vs sales tax) when I live in a state (WA) that doesn't have an income tax?

Well...we don't know exactly where you are seeing this...BUT

1)  WA residents who work cross-border in Oregon or Idaho will have state taxes withheld on their W-2 forms...so that could be it.  Those state withholding $$ count.

2) if you filed any tax form for another state last year (for 2021) and had to pay another state a final balance due during 2022 (but for 2021 taxes), then those $$ would qualify for a potential state income tax deduction this year....and those $$ would transfer into this year's forms automatically if you are in the same account you used last year.........if those $$ exist and are larger than the default WA sales tax....then that could be the reason.

3) Also possible, some $$ got put in the wrong box on (usually) W-2 or 1099-R forms, especially if you took a picture, or uploaded as a PDF file.  If you entered either of those form types, go back and edit each one to make sure the state boxes are entirely blank on each one..(boxes 15,16,17 on a W-2, or boxes 14,15,16 on a 1099-R).

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Those using desktop software could check their Tax Payments worksheet in Forms Mode to see where the $$ are coming from....but Online users would have to pay before printing out all their forms and worksheets to see that worksheet.