付给祖父母看孩子费用合法的，只是ｗ２雇主需不需要交税的问题。单亲家庭需要交税，双亲家庭不需要交税。

“Wages not counted. Do not count wages you pay to any of the following individuals as Social Security and Medicare wages, even if these wages are $1,800 or more during the year.

• Your spouse
• Your child who is under the age of 21
• Your parent. Exception — Count these wages if both the following conditions apply: A) Your parent cares for your child who is either under the age of 18, or has a physical or mental condition that requires the personal care of an adult for at least four continuous weeks in a calendar quarter. B) You marital status is one of the following: You are divorced and have not remarried; you are a widow or widower; or you are living with a spouse whose physical or mental condition prevents him or her from caring for your child for at least four continuous weeks in a calendar quarter.
• An employee who is under the age of 18 at any time during the year. Exception: Count these wages if providing household services is the employee’s principal occupation. If the employee is a student, providing household services is not considered to be his or her principal occupation.”

Note: In the third bullet point above, “count these wages” means do treat those wages as being subject to all payroll taxes.

In other words, you are responsible for paying Social Security and Medicare wages to your parents only if you are a single parent, or have a disabled spouse. When you only have one income and the extra 7.65% cost is a hardship, you have to pay the extra taxes. Who writes these laws?