Lump sum distributions are when the entire balance of an account is paid out at once. After you retire, you can elect to receive your money in a lump sum.
Of course, you will end up paying income taxes on the entire distributed amount that year. There is also what’s called the mandatory 20% withholding, which requires custodians to withhold 20% from retirement plan distributions if they are not part of a trustee-to-trustee transfer (such as funding an IRA).
If your tax bracket is lower than this 20%, you still must wait until April to get a refund. If this distribution is taken before age 59 ½, you may also have to pay the 10% IRS early withdrawal penalty.
There is an exception to that, if the account is sponsored by a company where the employee worked until age 55, distributions after that point are not subject to the early withdrawal penalty.
Another thing to keep in mind: if you take the entire amount out of your 401(k) account, and you deposit it into an investment vehicle that is not tax-advantaged, the money will no longer grow tax-free.