Washington Revised Code Title 4. Civil Procedure § 4.24.141. Action by another state to enforce tax liability--“Taxes” defined

(1) Any and all tax assessments lawfully made whether they be based upon a return or other disclosure of the taxpayer, upon information and belief of the taxing authority, or otherwise;

(2) Any and all penalties lawfully imposed pursuant to a tax statute;

(3) Interest charges lawfully added to the tax liability which constitutes the subject of the action.