Why is the total 401(k) contribution limit (employee + employer) so high?
"Because 401k's are also used by self employed. A person who has a schedule C profitable income can open a 401k and ""match"" in whatever ratio he wants, up to 25% of the net profits or the limits you stated. This allows self-employed to defer more income taxes to the future. Why only self-employed? Good question. Ask your congressman. My explanation would be that since they're self-employed they're in much more danger of not having income, especially later in life, if their business go south. Thus they need a bigger cushion than an average W2 employee who can just find another job." "Some 401k plans allow you to make ""supplemental post-tax contributions"". basically, once you hit the pre-tax contribution limit (17.5k$ in 2014), you are then allowed to contribute funds on a post-tax basis. Because of this timing, they are sometimes called ""spillover"" contributions. Usually, this option is advertised as a way of continuing to get company match even if you accidentally hit the pre-tax limit.  But if you actually pay attention to your finances, it is instead a handy way to put away additional tax-advantaged money.  That said, you would only want to use this option if you already maxed out your pre-tax and Roth options since you don't get the traditional tax break on contributions or the Roth tax break on the earnings. However, when you leave the company, you can transfer the post-tax money directly into a Roth IRA when you transfer the pre-tax money, match, and earnings into a traditional IRA."
Alright, team!   I found answers to part 1) and part 2) that I've quote below, but still need help with 3).  The facts in the article below seem to point to the ability for the LLC to contribute profit sharing of up to 25% of the wages it paid SE tax on.  What part of the SE tax is that?  I assume the spirit of the law is to only allow the 25% on the taxable portion of the income, but given that I would have crossed the SS portion of SE tax, I am not 100%.  (From http://www.sensefinancial.com/services/solo401k/solo-401k-contribution/) Sole Proprietorship Employee Deferral The owner of a sole proprietorship who is under the age of 50 may make   employee deferral contributions of as much as $17,500 to a Solo 401(k)   plan for 2013 (Those 50 and older can tack on a $5,500 annual catch-up   contribution, bringing their annual deferral contribution to as much   as $23,000). Solo 401k contribution deadline rules dictate that plan   participant must formally elect to make an employee deferral   contribution by Dec. 31. However, the actual contribution can be made   up until the tax-filing deadline.  Pretax and/or after-tax (Roth)   funds can be used to make employee deferral contributions. Profit Sharing Contribution A sole proprietorship may make annual profit-sharing contributions to   a Solo 401(k) plan on behalf of the business owner and spouse.   Internal Revenue Code Section 401(a)(3) states that employer   contributions are limited to 25 percent of the business entity’s   income subject to self-employment tax. Schedule C sole-proprietors   must base their maximum contribution on earned income, an additional   calculation that lowers their maximum contribution to 20 percent of   earned income. IRS Publication 560 contains a step-by-step worksheet   for this calculation. In general, compensation can be defined as your   net earnings from self-employment activity.  This definition takes   into account the following eligible tax deductions: (1) the deduction   for half of self-employment tax and (2) the deduction for   contributions on your behalf to the Solo 401(k) plan.  A business   entity’s Solo 401(k) contributions for profit sharing component must   be made by its tax-filing deadline. Single Member LLC Employee Deferral The owner of a single member LLC who is under the age of 50 may make   employee deferral contributions of as much as $17,500 to a Solo 401(k)   plan for 2013 (Those 50 and older can tack on a $5,500 annual catch-up   contribution, bringing their annual deferral contribution to as much   as $23,000). Solo 401k contribution deadline rules dictate that plan   participant must formally elect to make an employee deferral   contribution by Dec. 31. However, the actual contribution can be made   up until the tax-filing deadline.  Pretax and/or after-tax (Roth)   funds can be used to make employee deferral contributions. Profit Sharing Contribution A single member LLC business may make annual profit-sharing   contributions to a Solo 401(k) plan on behalf of the business owner   and spouse. Internal Revenue Code Section 401(a)(3) states that   employer contributions are limited to 25 percent of the business   entity’s income subject to self-employment tax. Schedule C   sole-proprietors must base their maximum contribution on earned   income, an additional calculation that lowers their maximum   contribution to 20 percent of earned income. IRS Publication 560   contains a step-by-step worksheet for this calculation. In general,   compensation can be defined as your net earnings from self-employment   activity. This definition takes into account the following eligible   tax deductions: (i) the deduction for half of self-employment tax and   (ii) the deduction for contributions on your behalf to the Solo   401(k).  A single member LLC’s Solo 401(k) contributions for profit   sharing component must be made by its tax-filing deadline. The best option for maximizing your money long-term is to contribute to the 401(k) offered by your employer. If you park your inheritance in a savings account you can draw on it to augment your income while you max out your contributions to the 401(k). You will get whatever the employer matches right off the bat and your gains are tax deferred. In essence you will be putting your inheritance into the 401(k) and forcing your employer to match at whatever rate they do. So if your employer matches at 50 cents on the dollar you will turn your 50 thousand into 75 thousand. "if you have 401k with an employer already, has the following features: Your contributions are taxed That's only true if you're a high income earner. https://www.irs.gov/retirement-plans/2017-ira-deduction-limits-effect-of-modified-agi-on-deduction-if-you-are-covered-by-a-retirement-plan-at-work For example, married filing jointly allows full deduction up to $99,000 even if you have a 401(k). ""the timing is just different"" And that's a good thing, since if your retirement tax rate is less than your current tax rate, you'll pay less tax on that money." To your question. Yes. What you propose is typically called the back door Roth. You make the (non-deductible) IRA deposit, and soon after, convert to Roth. As long as you have no other existing IRA, the process is simple, and actually a loophole that's still open.  If you have an existing IRA, the conversion may be partially taxed based on untaxed balance. As comments frequently get overlooked, I'm adding @DilipSarwate excellent warning regarding this - Depending on the value of the existing Traditional IRA and its   pre-existing basis, if any, the backdoor Roth conversion might be    almost completely taxable. Example: Traditional IRA worth $250K with    zero basis. New nondeductible contribution increase value to $255.5K    and basis $5.5K. Converting $5.5K into a Roth IRA leaves $250K in the   Traditional IRA with basis $5381.60. That is, of that $5500    conversion, only $118.40 was nontaxable and so, not only is the    original $5500 taxable income to the OP but he also owes taxes on    $5381.60 of that $5.5K conversion. In short, discussions of backdoor Roth conversions as a great idea should always be tempered with an acknowledgement that it does not work very well if there is any other money in the Traditional IRA. Once that nondeductible contribution enters a Traditional IRA, it does not come out completely until all your Traditional IRA accounts are drained of all money. All your Traditional IRA money is considered by the IRS to be in a single pot, and you can't set up a Traditional    IRA (possibly with a new custodian) via nondeductible contribution, convert just that Traditional IRA account into a    Roth IRA account, and claim that the whole conversion amount is nontaxable because all the tax-deferred money is in the other IRAs that you haven't touched at all. Last - you disclosed that you are depositing to a Roth 401(k) to the match. Which prompts me to ask if this is best. If your marginal rate is 25% or higher, you are missing the opportunity to save 'off the top', at that rate, and 'fill the lower brackets' at retirement, or, via conversion, any year before then when you are in a lower bracket for whatever reason. See my answer for Saving for retirement: How much is enough? which addresses this further.  From new comments - Won't his Roth 401k contributions max out his overall Roth   contributions? No. They are separate numbers, each with own annual limits. Wouldn't this prevent any back-door Roth conversions? The 401(k) has no effect on back door Roth, except for the fact that the 401(k) and high income make the Roth IRA unavailable by normal deposit. Back door is the only door.  At the end are you encouraging him to look for a Traditional 401(k) at   work to max out, then contributing to a Roth? Yes! Read the linked SE article, and consider the annual withdrawal that would get you to 25%. As I wrote, it would take $2M+ to 'fill' the 15% bracket at retirement. Are the $18,000 401k 2017 limit and the $5,500 IRA limit mutually exclusive for a combined limit of $23,500 (under 49)? Yes, but the amount that you can deduct from a traditional IRA depends on your gross income and marital status - See publication 590-A for details.  Also note that the limit applies to your combined traditional and Roth IRA contributions (meaning you can't contribute $5,500 to both; just a total of $5,500 between the two). I'm also assuming employee match $ count towards these limits - is this correct No - the limit for combined contributions between you and your employer is $54,000 in 2017.  So if you contribute $18,000 your employer can only contribute $36,000. "Calling this ""strange"" is an understatement. I'd call it illegal. You can't pay healthcare premiums with HSA funds while you are employed (unless you are on COBRA), and if you over contribute you pay a 6% tax on the overage unless you correct it. Furthermore, overage contributed by an employer must be treated as taxable wages, so they'd be better off just calling it a bonus and writing you a normal check. At least that way you wouldn't have to pay the 6% penalty on top of taxable wages." I question the reliability of the information you received.  Of course, it's possible the former 401(k) provider happened to charge lower expense ratios on its index funds than other available funds and lower the new provider's fees.  There are many many many financial institutions and fees are not fixed between them.  I think the information you received is simply an assumptive justification for the difference in fees. "In asnwer to your questions: As @joetaxpayer said, you really should look into a Solo 401(k). In 2017, this allows you to contribute up to $18k/year and your employer (the LLC) to contribute more, up to $54k/year total (subject to IRS rules). 401(k) usually have ROTH and traditional sides, just like IRA. I believe the employer-contributed funds also see less tax burden for both you and your LLC that if that same money had become salary (payroll taxes, etc.). You might start at irs.gov/retirement-plans/one-participant-401k-plans and go from there. ROTH vs. pre-tax: You can mix and match within years and between years. Figure out what income you want to have when you retire. Any year you expect to pay lower taxes (low income, kids, deductions, etc.), make ROTH contributions. Any year you expect high taxes (bonus, high wage, taxable capital gains, etc.), make pre-tax payments. I have had a uniformly bad experience with target date funds across multiple 401(k) plans from multiple plan adminstrators. They just don't perform well (a common problem with almost any actively managed fund). You probably don't want to deal with individual stocks in your retirement accounts, so rather pick passively managed index funds that track various markets segments you care about and just sit on them. For example, your high-risk money might be in fast-growing but volatile industries (e.g. tech, aerospace, medical), your medium-risk money might go in ""total market"" or S&P 500 index funds, and your low-risk money might go in treasury notes and bonds. The breakdown is up to you, but as an 18 year old you have a ~50 year horizon and so can afford to wait out anything short of another Great Depression (and maybe even that). So you'd want generally you want more or your money in the high-risk high-return  category, rebalancing to lower risk investments as you age. Diversifying into real estate, foreign investments, etc. might also make sense but I'm no expert on those."