Washington state set to impose that first ever income tax. It is called the millionaire's tax and it aims to tax those making more than a million dollars a year at a new rate of 9.9%. But it's not just the millionaires who are going to face this tax.In fact, couples whose combined income is a million dollars or more will also be taxed. Tax experts call it the marriage penalty. So, if you have two individuals who each make $600,000, neither would pay the state income tax if they filed as individuals.But if t ...