It is an annual tax if you create capital gains every year.

The measure passed in 2021 imposed a 7% tax on the sale of stocks, bonds and other high-end assets in excess of $250,000 for both individuals and couples.

The tax took effect Jan. 1, 2022. First payments are due on or before April 18.

and

Retirement accounts, real estate, farms and forestry were all exempt from the tax. Business owners were also exempt from the tax if they are regularly involved in running the business for five of the previous 10 years before they sell, own it for at least five years, and gross $10 million or less a year before the sale.

and

Under the new law, taxpayers could deduct up to $100,000 a year from their capital gains if they made more than $250,000 in charitable donations in the same tax year, something Huber cited in his ruling, noting that like “an income tax and unlike an excise tax, the new tax statute includes a deduction for certain charitable donations the taxpayer has made during the tax year.”

is all from an article linked from the article.

https://www.king5.com/article/news/local/olympia/supreme-court-ruling-capital-gains-tax-washington/281-ba3293e4-87b1-4965-bb41-b8e567080d0f