If you both work and you put Married-1 on your W-4 form when you are hired, you probably will end-up paying tax when you file your return. If you like to get refund rather than paying tax, you can have your employer withhold more on your paycheck following Married-0 or Single. The only difference is whether you want to pay more each paycheck and get a refund later or you want to pay less each payperiod and pay the rest with your return. Up to you.