<prompt> Human: Im trying to understand retirement accounts, but I think I have it mixed up. This is making it hard for me to determine by retirement strategy. Ill use simplified numbers here:Lets say my tax bracket is 10 this year and 20 when I retire. I make 100k in income this year and I will accrue 100k in capital gains by the time I retire. I can either contribute all 100k into a 401k or into a non-retirement brokerage account ignore roth accounts for now.Scenario 1 401k: I will pay no taxes on my income, but I will pay taxes on my withdrawal at retirement. As such, my total taxes for my income this year will be: 100k principle 0.2 taxes 100k capital gains 0.2 taxes 40k in taxesScenario 2 no 401k: I will pay taxes on my income this year, and I will pay taxes on my capital gains in the future. My total taxes will be: 100k principle 0.1 taxes 100k capital gains 0.2 taxes 30k in taxes. As such, if I know that my tax bracket will be higher when I retire, shouldnt I avoid a 401k?Assistant: Your math is ignoring marginal tax rates contrived example so I get it, but you need to factor them in - its usually efficient to fill up the cheap brackets in retirement, at least. Also ignoring the time value of the taxes saved by contributing to a traditional account now this obviously varies based on what you choose to do with it. Put another way, your 401k example costs you 100k today. Your taxable example costs you 110k today. You need to account for the other 10k and whether thats useful to you in one way or another.Im not sure if your situation cant occur and you might still end up better off as you think, but you need to account for these factors at least if you want a fair comparison.Human: You need to account for the other 10k and whether thats useful to you in one way or another.What do you mean?Assistant: Well, your 10k saved in taxes in the 401k example could be invested in a taxable investment account, earn 100 gains or we if thats the growth your example, and then youd end up with 10k extra gains -200 extra taxes for 9800 not counted in your example.Or it could be used to pay down debt, saved for other goals, etc. Its money, it has value, you need to factor it in and decide if you can make use of 10k today or not. Time value of money is a thing. Tax savings today have value, but it varies from person to person and situation to situation how much value it actually has.Human: Let me ask this: are there reasonable situations in which one may forego a 401k altogether?  <response>: Im sure theres a convoluted set of circumstances that could make it not make sense to use a tax-advantaged retirement vehicle entirely, but for 99 of people it makes sense to use it. 