Marriage will have significant financial consequences to the participant individuals. The impact on taxation is one of them. The following marriage tax calculator can help estimating the financial impact of marriage in terms of federal income tax. This calculator is only meaningful for the marriage of people who lives in the United States. This calculator is based on the 2017 tax brackets.
For tax purposes, you are considered married if you were married on the last day of the tax year. Likewise, if you are divorced by the last day of the year, you are considered unmarried for the whole year.
Marriage normally makes tax management more complicated than it was when you were single. It may bring some opportunities to save. Or, unfortunately, in many conditions, you have to pay more tax, which was called marriage tax penalty. The marriage tax penalty can be quite big if both of the participant individuals make high incomes, such as the marriage of two doctors. Or if one or both participant individuals make low income but receive tax credits, the combined income may disqualify the tax credits and therefore may end with marriage tax penalty. You may also find other conditions that will end with marriage tax penalty. However, considering one participant individual may stop working for reasons like childcare, unemployment, disability, early-retirement, etc., marriage may end up with tax benefit in long term even though you may see marriage tax penalty in short term.