"ASSUMING a person knows how to use and invest their money wisely" I'd ask if you were wise enough to beat the investments offered in your 401(k) after expenses, and with respect to the potential tax savings.
Then, since I'm a proponent of "deposit to the match, even if you have to eat rice and beans to find the cash to do" I'll extend the question to ask if you can beat the choices taking the match into account.
401(k)
- Your $1000 starts as $1500 and has a tax due on withdrawal years later.
AeroAccount - You start with $750 (after the tax) and might spend a decade before hitting $1500.
Start your own company?
That might be another story.
But to invest in the market and still beat the matched 401(k) takes a bit more wisdom than I'd claim to have.
money.stackexchange.com/users/187/JTP - Apologise to Monica
A 50% company match on your 401(k) is a huge amount of free money.
You'd have to absolutely crush the professional money managers to justify turning it down.
If you can do that, you should quit your job and do it full-time.
money.stackexchange.com/users/9116/solublefish
ASSUMING a person knows how to use and invest their money wisely, would it still be a bad idea to entirely disregard a 401k plan?
Yes.
A 401k, like an IRA, is a "qualified plan" and as such enjoys certain legal protections.
For a Roth 401k, the taxes are paid now and the interest accumulates tax free, and withdrawals will be tax-free.
Doing it on your own means that your own savings will have interest taxed as you earn it.
For a traditional 401k, current savings are deducted from current earnings, and the withdrawals will be taxed.
Doing it on your own loses the deferral of tax at this time.
Generally, 401ks and IRAs are highly resistant to judgements in civil lawsuits.
If you file for bankruptcy protection at any time in your working career, the assets in these accounts are immune (in most states) from being used to pay off your creditors.
If you do it on your own, that savings account will be emptied to pay off creditors in bankruptcy and also will be assets that can be taken from you in civil judgements (for example, you get in a car accident and they sue you).
You might never be sued, nor file bankruptcy in your entire life, but you are unnecessarily exposing yourself to risks: anything might happen in the next 50 years.
What you will lose in such circumstances far outweighs any perceived benefits you could possibly earn by rolling your own.
If you are the sort of person who can max out your 401k and IRA contributions each year, and still have a significant sum to set aside for savings, you should contact an investment advisor and attorney to see about protecting your assets.
money.stackexchange.com/users/7834/Tangurena
An experienced individual wouldn't ask such questions.
I don't say this to take a jab at you, but to provide context.
The matter is much more complicated than a simple answer to your question could accomplish.
The short answer is no, not necessarily; but it depends on the details.
Generally, if the employer matches, it's suggested that you take advantage of the match.
It's free money.
That said, it comes with some strings attached, like a vesting schedule.
It's not yours right away, necessarily.
Choices are limited in a 401k, but we should still come out ahead with that free money.
The investment choices available in a 401k are also a part of the details.
If they meet your needs you should certainly consider the 401k even if the employer doesn't match.
There is also the matter of one's particular tax situation, which is certainly an involved matter.
A 401k can certainly be a part of judicious tax planning.
It's a matter of working out the details.
Continuing this theme of details and coming back to the employer match: if the employer doesn't mach, I would make sure that I'm maxing out an IRA before considering the 401k.
If the employer matched, I would probably contribute to take advantage of that match.
However, it quickly becomes complicated here.
I'm accustomed to employer matching up to some percentage of pay, which typically works out to be less then the anual contribution limits for a 401k.
So, I my plan for such a situation is to contribute up to the employer match in the 401k, then max out an IRA, and then return to the 401k to finish contributing up to its yearly maximum.
There is plenty for you to consider in order to come up with a plan of action.
While it's certainly complicated, it's accessible to most people.
You don't have to be a genius.
In fact, eggheads are regularly trounced by the markets.
money.stackexchange.com/users/868/George Marian
Even ignoring the match (which makes it like a non-deductible IRA), the 401k plans that I know all have a range of choices of investment.
Can you find one that is part of the portfolio that you want?
For example, do you want to own some S&P500 index fund?
That must be an option.
If so, do the 401k and make your other investments react to it-reduce the proportion of S&P500 because of it(remember that the values in the 401k are pretax, so only count 60%-70% in asset allocation).
The tax deferral is huge over time.
For starters, you get to invest the 30-40% you would have paid as taxes now.
Yes, you will pay that in taxes on withdrawal, but any return you generate is (60%-70%) yours to keep.
The same happens for your returns.
money.stackexchange.com/users/5569/Ross Millikan
I would rather invest my money on my own how I see fit and plan my retirement custom-style.  ASSUMING a person knows how to use and invest their money wisely, would it still be a bad idea to entirely disregard a 401k plan?
Would any experienced individual balk at the idea of ignoring a 401k plan?
money.stackexchange.com
<united-states><401k>
money.stackexchange.com/questions/20436
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The question is whether you are wise enough at investing to beat the investments offered in a 401k and the tax savings. There are 401k plans that offer a range of investments.  Generally speaking no, but it depends on the details. You would probably lose more than you would gain and  you would need a lot of skill to beat the investments offered in your 401K after expenses. Choices are limited in a 401k, but we should still come out ahead with that free money as it is a "qualified plan" with certain legal protections. With a Roth 401k, taxes are paid now and interest accumulates tax free, and withdrawals will be tax-free. Doing it on your own means that your savings will have interest taxed as you earn it.   
Generally speaking no, but it depends on the details.  You would probably lose more than you would gain and  you would need a lot of skill to beat the investments offered in your 401K after expenses. Choices are limited in a 401k, but we should still come out ahead with that free money as it is a "qualified plan" with certain legal protections. With a Roth 401k, taxes are paid now and interest accumulates tax free, and withdrawals will be tax-free. Doing it on your own means that your savings will have interest taxed as you earn it.    If you are the sort of person who can max out your 401k and IRA contributions each year, and still have money set aside for savings, you should contact an investment advisor and attorney to protect your assets.  