I start a new job in May of 2019. I get married in October of 2019. What should my tax status be from May to October? Single? Married filing single?Married filing jointly? Is there any negative implications to choosing a married status from now until October, or is it in my best interest to file as single until I am legally married?
You cannot file a joint return if you are not legally married. If you are getting married in October of 2019 then next year when you prepare your 2019 return you can file married filing jointly. You can change your W-4 at work whenever you want to. That is just for your employer to tell them how much tax to withhold.