Question 1

When is a Traditional 401(k) mathematically better than a Roth IRA?

Accepted Answer

When your current marginal tax bracket during contribution years is higher than your anticipated effective tax bracket during retirement withdrawals, taking the immediate tax deduction delivers superior after-tax wealth.

Question 2

How does tax bracket arbitrage maximize retirement wealth?

Accepted Answer

By contributing pre-tax dollars at peak earnings (e.g. 24%-32% bracket) and withdrawing in lower retirement brackets (e.g. 10%-12% or standard deduction buffers), you capture the tax rate differential as pure profit.

Question 3

Can I contribute to both a 401(k) and a Roth IRA in the same tax year?

Accepted Answer

Yes. For 2026, you can maximize your employee 401(k) contribution limit ($23,500 + catch-up) while also funding a Roth IRA up to the statutory limit ($7,000 + catch-up), subject to MAGI phaseouts.

Traditional 401(k) vs Roth IRA Arbitrage

Investment & Tax Bracket Inputs

Spendable Wealth at Retirement

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