My spouse works part-time and qualifies for a 401k. She will make less than the $18,000 plus $6,000 catch up limit. So we want to put 100% of her earnings into the 401k. We understand OASDI and Medicare have to be paid. The payroll company is having a difficult time figuring this out. They want to allocate less than 100%, like 92.35% to cover the OASDI/Medicare but I am thinking this will also generate a federal tax and state tax liability, even if small.
What is best practice/proper procedure to accomplish goal?