That link is an excellent resource but I strongly disagree with the conclusion that taking the penalty in an IRA is better than investing in a taxable account. They do not consider that long-term capital gains are taxed at 15-20%, but in an IRA everything will be taxed as income, in addition to the 10% penalty. So if someone has a high tax rate and plans to hold positions for more than a year, taxable is the way to go.
The account balance used to create gains is already reduced by taxes though. So you pay taxes reducing the amount, get gains on that, then pay taxes on the gains. So the gains are effectively double taxed.
Which is better depends on the specific situation.
X dollars pre tax, tax rate of t
IRA: X
Post tax trading: X*(1-t)
Investment return: r
Gains:
IRA: X*r
PTT: X*(1-t)*r
Withdraw of gains:
(t+10%) for IRA (if the same tax rate, doing that for convenience)
15% for capital gains in PTT
IRA: X*r*(1-t-0.1) = X*r*(0.9-t)
PTT: X*(1-t)*r*(1-15%)=X*(1-t)*r*0.85=X*r*(0.85-0.85*t)
Difference: IRA - PTT
X*r*(0.9-t) - X*r*(0.85-0.85*t) = X*r*(0.9-t-(0.85-0.85*t))
=X*r*(0.9-t-0.85+0.85t)=X*r*(0.05-0.15t)
If 25% tax rate:
0.05-0.15*0.25=0.05-0.0375=0.0125=1.25% better return from IRA
If 37% tax rate:
0.05-0.15*0.37=0.05-0.0555=-0.0055=0.55% worse with IRA
20% cap gains:
PTT: X*(1-t)*r*(1-20%)=X*(1-t)*r*0.8=X*r*(0.8-0.8*t)
Difference: IRA - PTT
X*r*(0.9-t) - X*r*(0.8-0.8*t) = X*r*(0.9-t-(0.8-0.8*t))
=X*r*(0.9-t-0.8+0.8t)=X*r*(0.1-0.2t)
If tax rate is 25%: 0.1-0.2*.25=0.1-.05=0.05=5% higher return from IRA with penalty .
If tax rate is 37%: 0.1-0.2*.37=0.1-.074=0.026=2.6% higher return with IRA
So, in a high income situation, the penalized IRA gives better returns. Esp given the IRA contributions are at the marginal rate.