<prompt> Human: I know Roth is post tax i.e i dont pay tax retirement where as 401K is pretax I pay tax retirement and everyone seems to be sayingpay taxes now! so you dont have to!I dont get it.if i make 100K now and want to put 5 to 401K:100K - 5 95K.95K taxed at general 30 , Take home 66KOR i can do post tax roth IRA:100K taxed 30 70K, and then put 5 of that to Rothregardless of my total assets retirement 10M vs 100M vs 1Bif i take out only 100K, wont i only be taxed at the 100K level?  <response>: I think what you may be getting confused is with the tax on growth. The 5k you put into a traditional today pre-tax will, ideally, be worth a lot more than 5k when you go to take it out. You will owe income taxes on the money you take out when you withdraw under a traditional IRA at your tax rate at the time. If you put in 5k now and it grows to 20k in the future, you owe taxes on all 20k as you withdraw it. With a Roth, you pay taxes at your current tax rate before it goes into the account so it all grows tax free. If you put in 5k today and its worth 20k in the future, you just got 15k of tax free money. By the way, some companies offer both a Roth and a traditional 401k for employee contributions but all employer matching goes strictly into a traditional. 