Tax Rate

• The largest difference between single and married filing jointly filing statuses is the income tax rate. Single taxpayers are charged a higher income tax rate than married filing joint taxpayers. In many cases, the difference in tax rates is supposed to accommodate the higher incomes that dual income households have. In addition, the income thresholds that determine eligibility for various credits is higher for married filing jointly taxpayers.
  
  

Married Filing Separately

• If you are married and file separately from your spouse, your tax treatment is the same as a single taxpayer, with the exception of credit eligibility. Married filing separate taxpayers have the same tax rates as a single taxpayer. However, single taxpayers are allowed to take most credits offered by the Internal Revenue Service, provided other eligibility requirements are met. Married filing separate taxpayers may be unable to claim many tax credits that taxpayers that use other filing statuses may. Examples of credits unavailable to married filing separate taxpayers include the Earned Income Credit, Child Care Credit and Education credits. In addition, if your spouse itemized deductions, you may not claim any deductions -- itemized or standard -- which results in higher tax due.
  
  

Married, But Single

• If you are legally married, but meet certain criteria, you may be able to claim a single or head of household status instead of a married filing status. This is beneficial in scenarios where filing jointly creates a balance due, or eliminates eligibility for certain credits due to the high amount of combined income shown on the return. To be eligible for single status, you must live apart from your spouse for the last six months of the year or be legally separated. If you have dependent children, your children must live with you and you must pay more than half the cost of household expenses.
  
  

Filing Status Amendment

• You may file an amended return to change filing status if you find that you are eligible to claim an alternate status that is more beneficial for your tax scenario. You may change from any filing status to another, except you may not change from married filing jointly to another status. You may, however, change your filing status from single to married filing jointly. Changes must be made on IRS Form 1040X.