On March 24, 2023 the WA court filing shows the tax has been upheld as an excise tax.
https://www.courts.wa.gov/opinions/pdf/1007698.pdf
Even when it was in the state of unconstitutional, there was a stay on the ruling and the State had the right to keep collecting. Make sure to read the resources, because it is applied per transaction, not as a net LTCG.
https://dor.wa.gov/taxes-rates/other-taxes/capital-gains-tax
https://dor.wa.gov/taxes-rates/other-taxes/capital-gains-tax/do-you-owe-capital-gains-tax
"Amount
- Was your amount of Washington state long-term capital gains more than $250,000 after all exemptions, such as real estate or investments held in individual retirement accounts? See RCW 82.87.050.
If you answered Yes to the above question, you may owe Washington state capital gains tax."
"How are exemptions to the capital gains tax applied?
Exemptions from Washington’s capital gains are based on transactions. This means you may owe capital gains tax on some transactions and not on others."
"Deductions and exemptions
There are several deductions and exemptions available that may reduce the taxable amount of long-term gains, including an annual standard deduction of $250,000 per individual. In the case of spouses or domestic partners, the combined standard deduction is limited to $250,000 whether they file joint or separate returns."
