Many workers face a familiar choice this year: a pretax or Roth 401(k). What sounds simple can shape lifetime taxes. A lesser-known calculation, the break-even tax rate, is emerging as a practical way to choose.
The method compares a person’s current marginal tax rate with the rate they expect to face in retirement. If the future rate is higher, Roth contributions may win. If the current rate is higher, pretax could make more sense. The debate matters as employers expand Roth options and tax rules shift before 2026.
Background: Two Paths, Different Tax Timing
Pretax 401(k) contributions reduce taxable income today. Withdrawals in retirement are taxed as ordinary income. Roth 401(k) contributions do not reduce income today. Qualified withdrawals in retirement are tax-free.
The decision ties into changing policy. The 2017 tax law is set to expire after 2025. Without action, tax brackets may rise in 2026. That could raise future rates for many households. Meanwhile, SECURE 2.0 allows employers to offer Roth matches and made other changes to retirement plans.
For 2024, the employee 401(k) contribution limit is $23,000, with a $7,500 catch-up for those 50 and older. Higher earners should also watch income-related surcharges for Medicare and phaseouts that can push up marginal rates.
The Break-Even Tax Rate Explained
The break-even test asks a simple question: Is your marginal tax rate today higher or lower than your expected rate when you withdraw? It focuses on the rate that applies to your next dollar of income, not your average rate.
“It’s not easy to decide between pretax vs. Roth 401(k) contributions. But this lesser-known calculation could help you decide, experts say.”
Think of it this way. Pretax gives an upfront tax deduction at today’s rate. Roth gives a tax break later at the withdrawal rate. Comparing those rates can clarify the choice.
- If future rate > current rate: Roth often wins.
- If current rate > future rate: Pretax often wins.
- If rates are similar: Split contributions to both for flexibility.
Estimating Your Future Tax Rate
Forecasting retirement taxes is not exact, but key inputs help. Consider required minimum distributions from pretax accounts, Social Security timing, pensions, annuities, and withdrawals from brokerage accounts. Add state taxes if you plan to retire in a state with income tax.
Hidden thresholds can raise effective rates. Larger withdrawals can trigger taxes on Social Security benefits. Higher income can increase Medicare premiums through IRMAA surcharges. Capital gains harvesting in taxable accounts may interact with ordinary income.
Age, career stage, and location also matter. A new graduate in a low federal bracket may prefer Roth. A peak earner in a high bracket might benefit from pretax contributions now, then Roth conversions later in lower-income years.
Cases That Tilt the Decision
Several common situations influence the break-even rate. Workers expecting a large pension may face higher retirement brackets, favoring Roth. Small business owners with uneven income may find pretax best in high years and Roth in low years. Relocating to a no-tax state in retirement can tilt the math toward pretax now.
Parents seeking the Saver’s Credit or larger child tax credits may prefer pretax to reduce adjusted gross income. Borrowers on income-driven student loan plans may also use pretax to lower payments. Early retirees planning Roth conversions before age 73 may lean pretax during peak earning years and convert later in lower brackets.
How to Run a Quick Test
A simple worksheet can frame the choice without complex software. Use reasonable estimates, then revisit each year.
- Find your current marginal rate, including state taxes.
- Estimate retirement withdrawals and add Social Security, pensions, and taxable income.
- Check bracket thresholds, IRMAA tiers, and Social Security tax rules.
- Compare the future rate with your current rate.
- Adjust contributions toward Roth or pretax based on the result.
What Experts Are Watching
Advisers point to three variables. First, the fate of the 2017 tax law after 2025. Second, employer adoption of Roth matches, which could increase tax-free balances later. Third, market returns, which shape account size and future distributions.
They also stress cash flow. Roth contributions reduce take-home pay. Pretax increases it. A higher savings rate enabled by pretax can narrow or even flip the outcome. Fees, investment choices, and the option to do future Roth conversions should be part of the plan.
The break-even tax rate offers a clear lens on a complex choice. It is not perfect, but it brings the decision back to two numbers most people can estimate. For now, workers can run the test, split contributions if uncertain, and revisit after life changes. With tax rules set to shift in 2026, the case for reassessing each year is strong.
