Roth Conversion Pitfalls: Making Sure the Tax You Pay Today Is Worth It

Roth conversions can be one of the most valuable tools in a retirement plan. They can also create an unnecessary tax bill when the decision is based on an incomplete picture.

The appeal is easy to understand: pay taxes now, move the money into a Roth account, and receive tax-free withdrawals when the requirements are met. But tax-free withdrawals alone don’t tell us whether you’ll be better off.

We need to compare what you give up today with what you gain later.

My starting point is straightforward: look for opportunities to pay taxes at a lower rate than you would otherwise pay on those dollars. Then consider how the conversion affects the rest of your financial life, including your spending, investments, healthcare costs, and family.

Here are the pitfalls I look for when building that plan.

1. Converting simply because you have a long time horizon or expect high returns

A common argument is that Roth must be better if the money has decades to grow, especially if you expect strong investment returns.

That leaves out an important detail: the money used to pay the conversion tax could have remained invested, too.

Consider $7,000 already in a fully pre-tax IRA. Assume a hypothetical 25% tax rate both today and at withdrawal, with 10% annual growth for 35 years.

The after-tax result is the same.

This simplified example assumes identical investments and returns, qualified Roth withdrawals, no early withdrawal penalty, no interim distributions, and no other tax effects. The tax rate and investment return are illustrations, not a current tax bracket or a forecast.

Changing the growth rate or the number of years doesn’t change that basic relationship. When the tax rate is the same, taking out the same percentage before or after growth produces the same result.

That’s why I start with the tax-rate comparison. If you can pay less tax on those dollars now than you would later, a conversion becomes more attractive. If you’re likely to pay less later, waiting may be better.

Real retirement plans have more moving pieces. Paying the tax from outside the account, required distributions, and estate goals can all change the comparison. Those deserve analysis rather than being treated as minor exceptions.

2. Looking at this year’s tax bracket without looking ahead

A Roth conversion increases taxable income to the extent you convert pre-tax money. Whether that is worthwhile depends partly on what would happen if you left the money where it is.

You might be in a high bracket during your final working years, then have several lower-income years before Social Security, a pension, or required minimum distributions begin. Those years may offer a better opportunity to convert.

Other opportunities can arise during a sabbatical, a job transition, or a slower business year. But a low-income year isn’t automatically a good conversion year if you need your savings to cover expenses.

I want to compare several years together. How much income will you need? Which accounts will provide it? When will other income start? Are you planning to move to a state with different taxes?

The same reasoning applies to a high-income year. It may be sensible to wait, but a high tax rate today doesn’t automatically rule out a conversion if the future cost is likely to be even higher.

3. Waiting until RMDs begin to think about them

Clients sometimes ask whether I can help reduce a large tax bill caused by required minimum distributions, or RMDs.

Often, we would have had more flexibility if we had started planning years earlier.

If future RMDs are projected to create more taxable income than you need for spending, gradual conversions beforehand may help reduce that income and give you more control over future withdrawals.

It isn’t necessarily too late once RMDs begin. You can still convert eligible amounts beyond the required distribution, although the RMD itself cannot be converted. Roth IRAs have no lifetime RMDs for their original owners. [1]

The question is whether the benefit of reducing future required withdrawals justifies the tax you would pay now. Eliminating an RMD is not, by itself, proof that a conversion improves the plan.

4. Assuming your tax bracket captures the full cost

A conversion that fits within your current federal bracket can still be more expensive than it first appears.

Additional income can affect Social Security taxation, Medicare premiums, health insurance subsidies, capital gains rates, state taxes, and income-based deductions or credits.

Medicare is a good example of why timing matters. Income-related premium adjustments generally use your tax return from two years earlier. A conversion can therefore affect healthcare costs well after the year in which you complete it. [2]

Another distinction: a Roth conversion is not itself net investment income for the 3.8% Net Investment Income Tax. However, the additional income can cause more of your other investment income to become subject to that tax. [3]

I want to know the total additional cost of the conversion, including lost benefits or higher premiums, and compare it with the future costs it may help avoid.

Filling a tax bracket is a useful starting point for analysis. It isn’t automatically the best answer.

5. Ignoring the IRA aggregation and pro-rata rules

A separate IRA doesn’t necessarily give you separate tax treatment.

For this calculation, the IRS generally combines your traditional, rollover, traditional SEP, and traditional SIMPLE IRAs. Your spouse’s IRAs are separate, and inherited IRAs generally remain separate unless, for example, a surviving spouse treats one as their own. [4]

This matters when you have both pre-tax money and nondeductible contributions, also called after-tax basis.

Suppose you make a $7,000 nondeductible IRA contribution and convert $7,000. You also have $1 million remaining in pre-tax IRAs at year-end, with no other relevant distributions or adjustments.

Your after-tax share is approximately 0.695%: $7,000 divided by $1,007,000. Only about $49 of the conversion is tax-free; approximately $6,951 is taxable.

The remaining basis carries forward. It isn’t lost, but it must be tracked so you don’t pay tax on it again. Form 8606 is central to that recordkeeping. [4]

In some situations, an employer plan that accepts eligible pre-tax IRA rollovers can help address the issue before year-end. Check eligibility, plan costs, investment options, and timing first. After-tax IRA basis cannot simply be rolled into the plan with it. [5]

6. Confusing backdoor Roth planning with a waiting-period requirement

A backdoor Roth IRA generally involves making an eligible nondeductible contribution to a traditional IRA and then converting it to a Roth IRA. It can provide a route to Roth savings for someone whose income prevents a direct Roth IRA contribution.

The important details include contribution eligibility, the pro-rata calculation, any earnings before conversion, and accurate reporting.

There is no general IRS requirement to wait 12 months between the contribution and conversion. The separate one-rollover-per-year rule for certain IRA rollovers does not apply to Roth conversions. Custodians may still require contributed funds to settle or clear before processing a conversion. [5, 6]

Nor should an advisor use vague documentation to obscure the strategy. Keep clear records of what was contributed, what was converted, and how it was reported.

Waiting unnecessarily can allow taxable earnings to accumulate before conversion. The timing should follow the account’s actual requirements and your tax plan.

7. Overlooking an employer plan’s after-tax options

Some employer plans allow additional after-tax contributions and a way to move those dollars into Roth through an in-plan conversion or an eligible rollover. This is commonly called a mega backdoor Roth strategy.

After-tax contributions are different from regular Roth salary deferrals. Availability depends on the plan, and the amount you can contribute depends on applicable limits, compensation, employer contributions, and plan restrictions. [7]

I would usually review employer matching contributions, expensive debt, emergency savings, HSA eligibility, and standard retirement savings opportunities before committing additional money here.

For someone who can save more, though, this may be a useful option to consider alongside converting existing pre-tax assets. They solve different problems: one directs additional savings into Roth, while the other changes the tax treatment of money you already have.

8. Mishandling after-tax contributions and their earnings

After-tax contributions and the earnings on them do not have the same tax treatment. The contributions have already been taxed; the earnings generally have not.

An eligible employer-plan distribution can often be directed to different destinations, with after-tax amounts going to a Roth IRA and pre-tax amounts going to a traditional IRA or another eligible plan. [8]

That does not mean you can always withdraw only after-tax contributions and leave all associated pre-tax money behind. Distribution and allocation rules still apply.

Confirm the plan’s source accounting and rollover instructions before initiating the transaction. Also consider whether sending pre-tax earnings to a traditional IRA would complicate future backdoor Roth contributions.

Sometimes converting a small amount of earnings and paying the tax is reasonable. Avoiding every dollar of current tax isn’t necessarily worth creating a more complicated plan.

9. Choosing conversion timing without considering the trade-offs

A conversion can be completed all at once or in smaller amounts throughout the year.

A market decline may allow you to convert more shares for the same taxable dollar amount. But that doesn’t make an otherwise expensive conversion worthwhile, and the market can fall further afterward.

An early conversion places subsequent growth or losses in the Roth account. A later conversion gives you more information about your annual income and deductions. Spreading conversions out reduces dependence on one conversion date, but rising prices may mean converting fewer shares within the same tax budget.

One approach I consider is a barbell strategy: convert an amount early in the year that the plan comfortably supports, then fine-tune the total toward year-end.

This is about managing uncertainty. If the money was already invested in the traditional account, converting earlier does not create additional time in the market. It changes which account holds the investment during that time.

10. Assuming you can undo the conversion

Roth conversions used to be reversible through a recharacterization. That option is no longer available for conversions made after 2017. [9]

If the market falls after you convert, the tax calculation generally remains based on the value at conversion. An unexpected bonus or other income later in the year can also make the conversion more costly than anticipated.

That’s a reason to leave room for uncertainty when estimating the amount, particularly early in the year.

Regular IRA contributions may still qualify for recharacterization under the applicable rules. Contributions and conversions should not be confused.

11. Misunderstanding the five-year rules or the tax payment

There are two different five-year rules to understand for Roth IRAs.

For earnings to be withdrawn tax-free as a qualified distribution, the Roth IRA generally must satisfy the five-tax-year requirement and you must be at least 59½ or meet another qualifying condition. The clock begins with the first tax year for which you funded a Roth IRA; opening an empty account doesn’t start it.

Separately, each conversion has a five-tax-year period relevant to potential early withdrawal penalties on the taxable amount converted. Reaching age 59½ is an exception to that penalty. It does not eliminate the separate qualification requirement for tax-free earnings. [10]

Before converting, consider when you might need the money and where the tax payment will come from.

Paying the tax from checking, savings, or a taxable brokerage account can preserve more money inside the Roth. But that outside money has a purpose and an opportunity cost, too. Selling investments may create capital gains, and using cash may leave too little for spending or emergencies.

If IRA money is withheld for taxes, that portion does not reach the Roth and may incur an early distribution penalty if you are under 59½ and no exception applies. [11]

Paying from outside the account is often attractive, but compare both approaches using the same total resources. Also arrange any needed withholding or estimated payments rather than assuming the entire bill can wait until tax filing.

12. Looking only at taxes and overlooking the rest of the plan

A conversion may look appealing on a tax projection while leaving you less comfortable with the money available for the next few years.

I want the tax plan to support the spending plan. A larger Roth balance is not automatically an improvement if the upfront tax reduces the flexibility you need today.

Family and estate goals matter as well. The relevant comparison may include your spouse’s future tax situation or the taxes beneficiaries could pay. Estate-tax interactions deserve their own analysis rather than a blanket assumption that one account type is always better.

Account protections also deserve attention before moving money out of an employer plan. ERISA-covered plans generally have strong creditor protections. IRAs have protections too, but the details can differ between bankruptcy and other claims, and by state and source of funds. A rollover does not automatically eliminate protection. [12]

If those protections matter to your situation, review them before moving the money and consider whether the plan permits a suitable Roth conversion within the plan itself.

How I put this together

I start with your retirement income needs and compare the plan with and without conversions. Then I look at different amounts, timing, and sources for the tax payment.

The question I want to answer is whether paying this tax now helps you make more of your money over time, while preserving the spending and flexibility that matter to you.

Sometimes that means a series of annual conversions. Sometimes it means a smaller amount than the tax bracket would allow. Sometimes the best decision is to leave the pre-tax money where it is.

Effective financial planning brings these decisions together. Run the numbers, understand the trade-offs, put the plan in writing, and adjust as your life and the rules change.

If you’d like help understanding how Roth conversions fit into your retirement plan, feel free to reach out at Peter@ShammasFP.com or schedule a conversation.

This article is for educational purposes. Examples are hypothetical. Tax treatment depends on your circumstances and applicable law.

Sources

1. IRS: Retirement plans FAQs regarding IRAs and Required minimum distributions.
2. Social Security Administration: Medicare premiums.
3. IRS: Questions and answers on the Net Investment Income Tax.
4. IRS: Instructions for Form 8606.
5. IRS: Publication 590-A.
6. Fidelity: All about the Roth, backdoor Roth discussion; Roth conversion process.
7. Fidelity: Backdoor Roth and Roth conversions explained; IRS: Publication 560.
8. IRS: Rollovers of after-tax contributions in retirement plans.
9. IRS: Topic 309, Roth IRA contributions.
10. IRS: Publication 590-B, Roth IRA qualified distributions and early distribution rules.
11. IRS: Topic 557, Additional tax on early distributions.
12. U.S. Department of Labor: What you should know about your retirement plan.