After you file

IF it is the Portland OR, "Arts Education and Access Income Tax (Arts Tax)"

.....I don't see that Oregon includes that City tax in their state forms.

.....TTX does work with a few City forms in a couple other states, but Portland would have to establish communications with, and form preparation with, ALL of the tax software providers if they (Portland) wanted to receive the Arts tax thru any of  the yearly personal income tax returns.  Apparently, they have not done so.

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Someone else may have more detailed information, but from what I see, it must be paid separately from your Fed&OR income tax returns, either  Online at  the Portland tax website, or on paper using their downloadable forms.

https://www.portlandoregon.gov/revenue/60076

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Perhaps talk to some long-time Portland resident.....a neighbor or at-work for details about how this is really supposed to be paid.