Yes, the actual taxes withheld and paid on your 401k withdrawal may not be sufficient to cover the income tax when you take all of your income into account. Therefore, you may owe some additional income tax that was not expected. Additionally, if the distribution is considered to be an 'early' distribution without a valid exception, you may also owe a 10% penalty tax.
You will receive a Form 1099-R that reports the details of your distribution. This form will be entered into your return to determine the tax impact. The entire distribution is considered to be income to you, not just the remaining portion that you actually received after income tax was withheld.
Take a look at the following TurboTax help articles to learn more:
What are the exceptions to the penalty for an early withdrawal from my 401(k)?
How does a retirement plan withdrawal affect my taxes?
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