Break-Even Tax Rate (BETR)

What Is the Break-Even Tax Rate (BETR)?

The break-even tax rate, or BETR, is the future marginal tax rate that would make an investor roughly indifferent between converting a traditional IRA to a Roth IRA now or leaving the assets in pretax form. In retirement-tax planning, the usual rule of thumb, compare today's tax rate with your expected future tax rate, can be too simple. BETR tries to identify the future tax rate at which the investor's after-tax outcome would be about the same either way.

That makes BETR a decision threshold, not a tax rate you report on a return. It is a planning tool for evaluating a Roth IRA conversion more carefully than a rough headline-bracket comparison would allow.

Key Takeaways

• BETR estimates the future marginal tax rate that makes a Roth conversion and a no-conversion path roughly equivalent.
• It is more useful than a simple current-versus-future tax-rate comparison when conversion taxes can be paid from outside the IRA.
• BETR can be lower than the current marginal tax rate, which means a conversion may still make sense even if the investor expects a somewhat lower future rate.
• Investment horizon, taxable-account funding, and IRA basis can all change the BETR.
• BETR is a planning framework, not a guarantee that one path will be better under every future tax-law or market scenario.

How BETR Works

BETR asks a focused question: at what future marginal tax rate would an investor be indifferent between paying conversion tax now and keeping the future growth in Roth form, versus avoiding conversion now and paying tax later when the money is eventually withdrawn? If the investor expects the actual future marginal rate to be above that break-even point, the conversion may look more attractive. If the investor expects the future rate to be below it, leaving the money pretax may look more attractive.

The framework is helpful because a conversion does more than accelerate tax. It can also move future growth from a taxable or tax-deferred setting into a tax-free setting. That means the current tax bill is not the only variable in the decision.

How BETR Shapes Roth Conversion Decisions

BETR shapes Roth conversion decisions because many investors stop at a simplistic comparison: convert only if your future tax rate will be higher than your current tax rate. That framing misses the fact that the source of the tax payment matters. If conversion tax is paid from money outside the IRA, the investor may be able to move more assets into Roth status and keep more future compounding sheltered from taxation.

As a result, the break-even future tax rate can be lower than today's marginal rate. In other words, the conversion can still improve after-tax wealth even when the investor does not expect a dramatically higher tax rate later.

What Can Move the BETR

Several planning variables can change the BETR. A longer investment horizon can make conversion more attractive because more future growth happens under Roth treatment. Paying conversion tax from a taxable account instead of from the IRA can also lower the BETR because more retirement assets remain inside the Roth after the transaction. Existing basis in the traditional IRA can lower the BETR too, because not every dollar converted is fully taxable.

The result is that BETR is not a universal constant. It is specific to the investor's tax situation, account mix, time horizon, and assumptions about future growth and future withdrawals.

BETR Versus Current Marginal Tax Rate

The current marginal tax rate tells you what rate applies to the next dollar of conversion income today. BETR tells you the future marginal rate that would make the conversion decision roughly neutral on an after-tax basis. Those are related, but they are not the same thing.

This distinction is why BETR can provide a more useful conversion threshold than a simple comparison of today's bracket with a guessed retirement bracket.

Using BETR in the Roth IRA Conversion Calculator

The Roth IRA Conversion Calculator uses the BETR idea to show the future tax-rate threshold for the conversion scenario you enter. The calculator also keeps the surrounding assumptions visible, including the conversion amount, tax-payment source, cash yield, time horizon, and estimated future taxable income.

That matters because BETR is most useful when it is read with the assumptions that produced it. A lower break-even rate can make a conversion look more flexible, but the conclusion still depends on whether the tax cost, investment horizon, and future tax picture are realistic for the household.

How a Break-Even Tax Rate Still Remains a Framework

BETR improves the question, but it does not remove uncertainty. Future tax law can change. Actual withdrawal timing may differ from today's assumptions. Portfolio returns may be higher or lower than expected. The investor's effective tax rate in retirement may also differ from the marginal rate that matters for conversion analysis.

BETR works best as a planning lens rather than a rigid formula. It helps investors ask a better conversion question, but it still depends on judgment and assumptions.

Example Conversion Still Making Sense Below Today's Tax Rate

Suppose an investor is considering a Roth conversion at a current 24 percent marginal tax rate. If the investor calculates that the BETR is 20 percent, the conversion could still make sense even if the investor expects a somewhat lower future marginal rate than 24 percent. The reason is that the Roth structure may still create enough future tax benefit to outweigh paying conversion tax now.

The Bottom Line

The break-even tax rate is the future marginal tax rate that would make an investor roughly indifferent between converting a traditional IRA to a Roth IRA now or leaving the assets pretax. It gives Roth conversion analysis a more useful threshold than a simplistic current-versus-future tax-rate comparison and better reflects how account structure, tax-payment source, and future compounding affect the decision.