Converting a 401K to a Roth IRA involves certain costs that individuals should consider. When you convert a traditional 401K to a Roth IRA, you will need to pay taxes on the amount converted. This is because traditional 401K contributions are made with pre-tax dollars, while Roth IRA contributions are made with after-tax dollars. The amount converted from the 401K to the Roth IRA is treated as taxable income in the year of the conversion. Additionally, if you are under the age of 59 ½ and have held the Roth IRA for less than five years, you may be subject to a 10% early withdrawal penalty on the converted amount. It's important to consult with a financial advisor or tax professional to understand the specific tax implications and costs associated with converting a 401K to a Roth IRA in your individual situation.