Final answer:
The false statement about married, filing jointly status is that filing a joint return avoids the marriage penalty. This can occur when jointly filing spouses pay more tax than if they filed separately. Other statements about amendments and joint and several liability are true.
Step-by-step explanation:
The statement among the options that is false regarding the married, filing jointly status is the first one: Filing a joint return avoids the marriage penalty. The marriage penalty can occur when two individuals filing jointly pay more tax than they would if they were single and filed separately, particularly when both spouses earn similar incomes. It's essential to understand that marital status is determined as of the last day of the tax year, meaning that being married on December 31 means you are considered married for the entire year.
It is also true that once a joint return has been filed and the due date has passed for a particular year, the spouses cannot switch to separate returns for that year. However, for those who are married and file separately, it is possible to later amend and file a joint return together. Lastly, filing jointly does indeed carry the potential disadvantage of joint and several liability, where each spouse is equally responsible for the tax and any interest or penalty due on the joint return.