401ks aren't taxed on withdrawl either, that isn't where HayGan is getting the double tax.
Let's say I take out $10,000 from my 401k as a loan - I won't be taxed on that loan.
Now I pay it back - with after tax income - so - lets say thats a 25% tax rate - I have to earn $12,500 to pay that money back - and I now have that $10k back in my 401k.
Now when I retire and take money out of that 401k, I pay taxes on it - because I supposedly didn't earlier. There is no provision for "except for this money here which we already taxed." So I'm still at that 25% bracket (just to make things easy) and need $10k, I have to take out $12,500.
So the government has gotten $5000 from me in taxes when if I hadn't borrowed they would have only gotten $2500.
Thats a pretty heavy penalty.
There are many reasons not to borrow the money but i think the double taxation is a rumor that is not mathematically correct.
You end up in the same tax situation either way. When you take the 10,000 you get to buy something worth 10,000. If you had not put the 10,000 in your 401 you would have paid taxes and put it in the bank but only had 7500in the bank. You would have to come up with 2500 more to buy what you want. yes you pay back with 10,000 that was 13,000 before taxes, but if you had never used the 401 you would have had to earn 13333 to come up with the 10,000 you need anyway.
Let's say I earn 23,333. I put 10,000 in my 401K, i pay no taxes on the way in. On the other 13,300 i pay 25% which leaves me with 10,000 in the bank.
now i decide that i want to buy something that is 10,000. I can spend the 10,000 in the bank. later when i take the 10,000 out of my 401 I will pay the 2500 in taxes on that and be able to buy a 7500 item. So the 2 items cost me 2500+3333 (5833) in taxes.
In option 2 i earn 23,333 and do the same thing putting 10,000 in 401 and paying 3333 in taxes to have 10,000 in the bank. Later, i decide to buy something but i use a loan and take the 10,000 from my 401K i pay it back with the 10,000 that i had in the bank. I still have 10,000 in the 401k. when i take that out later i pay 2500 in taxes. Again I have the same 2 items and paid the exact same tax of 5833. (2500+3333).
In option 3 i earn 23,333 and put none of it in a 401. I pay 25% in taxes which is 5388. I am left with 17500 to buy my 10,000 and 7500 same 2 items.
Ignoring interest and inflation, there is no double taxation to using a 401K loan.