I withdrew from my 401k in 2021. I had them hold 11% of my 401k for tax reasons. Will I need to pay back when I include it on my return?

[Critter-3]

Only 11% ?   That may not be enough to cover the taxes and if you are not 59.5 or older the 10% penalty. 

[rjs]

The tax is not calculated separately for your 401(k) withdrawal. Whether you have a payment due on your tax return depends on your total income, total tax, and total withholding for the year. Everything is combined.

[Opus 17]

The withheld amount is only an estimate, and may in fact be too low.  You file one tax return for the year that reports all your income and calculates your tax.  You get credit for all your withholdings and payments, and if you paid more than you owe, you get a refund, and if you paid less than you owe, you will owe an additional tax payment.  

Most taxpayers will pay 12% or 22% income tax.  If you are under the age to make a qualified withdrawal, you will also owe a 10% penalty.  Plus any state income tax.  So depending on your total income and total payments, you may end up short.  But you will get credit for the withheld amount.