Roth vs Traditional Solo 401(k): The Bracket Math Nobody Explains
Conventional wisdom: Roth if young, Traditional if old. Real answer: compare your current marginal rate to your expected retirement marginal rate. If retirement rate is higher, Roth wins.
The Roth vs Traditional debate generates more bad takes than almost any other personal finance topic. Most internet advice ranges from "always Roth" to "always Traditional" based on the writer's age. The actual answer is one comparison.
The single equation
Compare your current marginal federal + state tax rate to the marginal rate you expect on your retirement withdrawals. If the future rate is higher, Roth wins. If the current rate is higher, Traditional wins. Same rate is a wash; pick based on flexibility.
What "expected retirement rate" actually means
People often anchor to today's brackets and assume retirement income will be lower. Two pitfalls. One: tax brackets change. The 2017 Tax Cuts and Jobs Act sunsets in 2026, so today's 22% may revert to 25%. Two: most savers underestimate how much income they'll need. A retiree withdrawing 4% on a $1.5M portfolio plus Social Security and a pension is often pulling $80k-$100k of taxable income, solidly in the 22% bracket once standard deduction is applied.
The current bracket reality
For 2026 the brackets are: 10% up to $11,925, 12% to $48,475, 22% to $103,350, 24% to $197,300, 32% to $250,525, 35% to $626,350, 37% above. Most freelancers in their peak earning years sit in 22% or 24%. So the question becomes: do you expect retirement income to push you into 22%-plus territory? For middle-class savers with no pension, often yes.
The hidden Roth advantage
Roth Solo 401(k) accounts have no required minimum distributions starting in 2024 (SECURE 2.0). So a Roth Solo 401(k) lets you compound tax-free forever, useful for estate planning. Traditional accounts force you to start withdrawing at 73 (75 if born after 1960), which can push you into a higher bracket exactly when you didn't want it.
Practical splits
Most planners suggest splitting employee deferral 50/50 Roth and Traditional if you're in the 22-24% bracket and uncertain. The employer share is forced Traditional pre-tax anyway (until provider Roth support catches up to SECURE 2.0).
The mega backdoor angle
Some Solo 401(k) providers (mySolo401k, Carry, others) support after-tax non-Roth contributions plus in-plan Roth conversions, opening a "mega backdoor Roth" path. This pushes Roth dollars beyond the $23,500 employee deferral cap up to the $70,000 combined ceiling. Worth investigating only if you're maxing the standard $23,500 already and want more Roth-flavored room.
State tax wrinkle
Living in California (high state tax) and planning to retire in Florida (zero state tax)? That's a strong argument for Traditional now (deduct against 9.3% state) and pay zero state tax on the eventual withdrawal. Reverse the move and Roth wins.