How Does a Roth In-Plan Conversion Work?

A Roth in-plan conversion allows employees to shift pre-tax retirement savings within an employer-sponsored plan, such as a 401(k), into a designated Roth account. This process triggers immediate taxation on the converted amount, but future qualified withdrawals become tax-free. Many workplace retirement plans offer this option, though rules vary by employer. Converting pre-tax funds to Roth status helps those expecting higher income in retirement or seeking to minimize future tax liabilities.

A financial advisor could help you optimize your retirement investments to minimize your tax liability. 

What Is a Roth In-Plan Conversion?

A 401(k) in-plan Roth conversion lets participants transfer rollover-eligible funds to a designated Roth account within the same plan. This allows your money to grow tax-free, as opposed to tax-deferred, for years or even decades.

One rule is that the conversion of this money is a taxable event. Taxes apply to investment gains and any pre-tax contributions included in the conversion. The account owner must report the taxable portion of the conversion as gross income in the year of conversion. This taxable income does not incur the usual 20% withholding or the 10% mandatory penalty. ¹

A second rule mandates that you are vested in the Roth account for a minimum of five years. Otherwise, the Roth account is not available for an in-plan conversion.

When Is a Roth In-Plan Conversion Helpful?

If you are young and in a lower tax bracket, a Roth in-plan conversion could lower your tax liability. If you anticipate future tax rates to be higher, this is also a reasonable tax strategy to undertake.

Start making Roth in-plan conversions since you pay taxes on the conversions at your current, ordinary income tax rate. It may be cheaper for you to take this strategy compared to paying taxes on conversions later at a higher tax rate. Remember that you have to be vested in the Roth account for five years. You could accumulate decades of tax-free money for yourself, your spouse or your children.

If you have deductions, such as high medical expenses, that allow you to itemize in the tax year you make a Roth in-plan conversion, the conversion could be even more financially advantageous. Your itemized deductions would help offset the tax liability.

Avoiding RMDs

A Roth in-plan conversion also works if you are a high-net-worth individual and your retirement savings don’t need to support your spending needs in retirement. Roth accounts are not subject to required minimum distributions (RMDs), so they do not force taxable withdrawals at age 73. You can make an in-plan conversion and your money can grow tax free as long as you follow the rules.

Other Considerations

If you anticipate moving to a state with higher income taxes a Roth in-plan conversion might make sense. If market declines have reduced your retirement portfolio’s value a Roth in-plan conversion could reduce your annual tax liability.

When Not to Take a Roth In-Plan Conversion

If you are a high-income individual and you are nearing retirement, a Roth in-plan conversion may not make financial sense. You should look at your tax bracket now and your anticipated tax bracket after retirement. Make sure to include all other sources of retirement income like Social Security, too. This will help determine whether you should make a Roth in-plan conversion. You would then only do so if your tax bracket is expected to be higher in retirement.

Avoid a Roth in-plan conversion if you lack extra funds outside your retirement accounts to cover the tax bill. Otherwise, any tax savings on the conversion that you realize after retirement will not outweigh having to produce the money to pay a huge tax bill now.

How to Report a Roth In-Plan Conversion

A Roth in-plan conversion is a taxable event that must be reported on your federal income tax return. The amount converted from a pre-tax retirement account to a Roth account is treated as ordinary income in the year of conversion. Your employer will issue a Form 1099-R, which details the converted amount and any applicable taxes withheld.

When filing your taxes, enter the taxable portion from Form 1099-R on Form 1040, Line 5b (or the equivalent for the applicable tax year). If no taxes were withheld, you may need to make estimated tax payments or adjust withholding to avoid underpayment penalties.

While Roth accounts grow tax-free, failing to report a conversion properly could result in IRS penalties. Keeping detailed records of converted amounts and any associated tax payments can help prevent filing issues.

How Much to Convert and When: A Practical Framework

The most practical starting point is your current tax bracket. Before deciding on a conversion amount, calculate your total expected income for the year and identify how much room remains before crossing into a higher bracket. That figure sets a natural limit on what you can convert without increasing your marginal rate.

If your taxable income already puts you near the top of your bracket, a large conversion in that same year could push a meaningful portion into a higher rate. In that case, a smaller conversion or waiting for a lower-income year may produce a better outcome.

Timing matters as much as amount. The period between retirement and the start of RMDs or Social Security is often the most favorable window for conversions. Income tends to be lower during this stretch, which means the IRS taxes the converted amount at a lower rate. Years with unusually high deductions, such as significant medical expenses or charitable contributions, can also offset some of the conversion’s tax impact.

Converting a large balance all at once is rarely the most efficient approach. Spreading the total across several years keeps each annual conversion within a manageable tax range and gives you the flexibility to adjust based on changes in income, deductions or tax law. It also reduces the risk of triggering secondary consequences, such as increasing the taxable portion of Social Security benefits or pushing modified adjusted gross income above the Medicare IRMAA thresholds, which can raise Part B and Part D premiums the following year.

The goal is not to avoid taxes on the conversion entirely. It is to pay them at the lowest rate available to you given your full financial picture in any given year.

Bottom Line

A Roth in-plan conversion is a strategy that retirement investors can use to limit tax liability and generate increased tax-free income for the future. While a conversion could help you save money, you should also note that there are times when it may not benefit you financially and you may want to consult a financial advisor to see how it fits into you overall retirement strategy.

Tools for Retirement Planning

• A financial advisor can help you create a tax strategy for your retirement income. Finding a financial advisor doesn’t have to be hard. SmartAsset’s free tool matches you with financial advisors who serve your area, and you can have a free introductory call with your advisor matches to decide which one you feel is right for you. If you’re ready to find an advisor who can help you achieve your financial goals, get started now.
• Would you like an estimate of how much you will need to retire? Check out SmartAsset’s retirement calculator to get your estimate based on your individual circumstances.
• If you want to know how much guaranteed income you will have for retirement, SmartAsset’s free Social Security calculator can help you estimate your future benefits.

Photo credit: ©iStock.com/insta_photos, ©iStock.com/cokada, ©iStock.com/Prostock-Studio