I am converting money from my 401K to my ROTH IRA. How much money should I have withheld for taxes?

[macuser_22]

That depends on what your marginal tax rate (including the 401(k) distribution) will be.   The mandatory  401(k) Federal withholding is 20%.   If you expect to be in a higher tax bracket then withhold more.   Also figure state tax if any for state withholding.

[SweetieJean]

Assuming it's Traditional (not Roth) 401(k), that depends upon your marginal tax rate. Also note that any increase in income can make (for example) more of your Social Security income taxable, affect Medicare premiums two years down the road, lower or eliminate some deductions/credits, etc.  Try using this tool for estimating:

https://turbotax.intuit.com/tax-tools/calculators/taxcaster

And remember State taxes.

[Critter]

If this is a 401K conversion to a ROTH then you should have NOTHING withheld...instead you should pay in from withholding some other place OR make an estimated payment. 

If you have withholding from the conversion not all will be sent to the ROTH & the portion withheld will become a taxable distribution. Not the best choice. 

[macuser_22]

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@Critter wrote:

If this is a 401K conversion to a ROTH then you should have NOTHING withheld...instead you should pay in from withholding some other place OR make an estimated payment. 

If you have withholding from the conversion not all will be sent to the ROTH & the portion withheld will become a taxable distribution. Not the best choice. 

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True, but whatever the source of the money to pay the tax it will be from after-tax money that you already paid tax on.

[dmertz]

A significant problem with using withholding from the 401(k) distribution to pay the taxes on the Roth rollover without replacing them to complete the rollover of the entire distribution is that it results in a lower balance in the Roth IRA available to grow tax free.  It usually best to roll the entire distribution over to the Roth IRA and pay the taxes with funds other than those presently in a taxable qualified retirement account.