Roth Conversion: How It Works

What a conversion is, and what it is not

Converting means moving amounts that have never been taxed into an account where future qualified distributions are treated differently. The conversion itself is a taxable event: pre-tax amounts moved into a Roth account are generally included in gross income for the year of the distribution, and the tax is due for that year like any other income.

A rollover and a conversion are distinct transactions even though the paperwork can look similar. Moving pre-tax plan money into a traditional IRA is a rollover and is generally not taxable. Moving designated Roth plan money into a Roth IRA is also generally not taxable, because those amounts were already included in income. Moving pre-tax money into any Roth account is a conversion, and that is where the tax arises.

Several routes lead to a Roth account. A traditional IRA can be converted to a Roth IRA. Pre-tax amounts in an employer plan can be rolled directly to a Roth IRA, which is treated as a conversion. Some plans permit an in-plan Roth rollover, which moves pre-tax plan money into a designated Roth account inside the same plan. SEP and SIMPLE IRAs can be converted as well, though SIMPLE IRAs have a waiting period after the first contribution that has to be satisfied first.

When people typically look at this

Circumstances rather than rules bring conversions into the conversation. Years with unusually low taxable income — an early retirement before required distributions begin, a gap between jobs, a year with large deductions — are the most commonly examined, because the conversion is taxed at whatever rate applies to that year.

Account structure drives interest as well. Someone holding a large pre-tax balance may look at conversions in the context of future required distributions, beneficiary planning, or a desire to hold part of their savings in an account with different distribution rules. None of those observations establishes that a conversion is appropriate in a given case.

The reason this page stops short of a recommendation is that the answer depends on facts it cannot see: your marginal rate this year and in future years, your state’s treatment of the income, the source of the money used to pay the tax, your time horizon, and your beneficiaries’ situations. A qualified tax professional working from your actual return is the appropriate place for that analysis.

• A year with unusually low taxable income compared with prior or expected years
• Retirement before the age at which required distributions begin
• A large pre-tax balance relative to expected future withdrawals
• A separation from employment that makes plan money available to move
• Beneficiary and estate considerations involving different distribution rules

What to establish before converting anything

Total pre-tax IRA balances come first, and the total means all of them. Traditional, SEP, and SIMPLE IRAs are generally aggregated when determining how much of a conversion is taxable, so a single account does not tell the story. Any after-tax basis in those IRAs should be documented on the Form 8606 filings that track it.

The tax payment itself needs a source. Tax on a conversion is generally owed for the year of the conversion, whether or not any money was taken out to pay it, and using converted funds to cover the tax reduces the amount that ends up in the Roth account — with additional consequences before age 59½. Confirming how the payment will be made, and whether estimated tax payments are required to avoid an underpayment penalty, belongs in the preparation rather than the aftermath.

Timing constraints round out the list. Required minimum distributions cannot be converted and generally must be satisfied first for anyone at that stage. A conversion is attributed to the year the distribution occurs, which makes late-December conversions operationally tight. Whether your plan permits an in-plan Roth rollover, and whether you already have a Roth IRA with an established five-year period, are both facts to confirm rather than assume.

• Combined balances across all traditional, SEP, and SIMPLE IRAs
• Any after-tax basis in those IRAs, with the Form 8606 history that supports it
• How the tax will be paid, and whether estimated payments are needed
• Whether a required minimum distribution must be taken before converting
• Whether your employer plan permits an in-plan Roth rollover
• The first year any Roth IRA of yours was funded

The range of choices

Converting is not binary. Partial conversions are permitted, conversions can be spread across multiple tax years, and a decision to convert nothing is a complete answer. The size and timing of each conversion are the variables people actually control.

Adjacent transactions are worth distinguishing so they do not get conflated. Rolling pre-tax plan money to a traditional IRA keeps its pre-tax character and leaves the conversion question open for later. Taking a cash distribution is neither a rollover nor a conversion — it is taxable income that leaves the retirement system entirely.

• Convert nothing and leave pre-tax amounts as they are
• Roll pre-tax plan money to a traditional IRA without converting, keeping the option open
• Convert part of a balance this year and reassess in future years
• Convert in stages across several tax years
• Use an in-plan Roth rollover, if the plan permits it
• Take a taxable distribution instead, which is not a conversion and leaves the retirement system

How a conversion is executed

Custodian mechanics are usually simple. A conversion between accounts at the same custodian is often a form or an online instruction; a conversion involving two institutions is handled as a distribution from the traditional account and a conversion contribution to the Roth account, generally moved directly between the two.

Withholding deserves a deliberate decision rather than a default. Electing withholding from the converted amount means less money arrives in the Roth account, and the withheld portion is itself treated as a distribution that was not converted — which can carry additional tax before age 59½. Paying the tax from funds outside retirement accounts avoids that, though it requires having the money available.

Reporting follows a predictable pattern. The distributing custodian issues a Form 1099-R, the receiving custodian reports a conversion contribution, and the taxable amount is calculated on your return, with Form 8606 handling basis where after-tax amounts exist. Keeping the year-end statements and the 8606 filings together is what makes future distributions straightforward to report.

• Confirm the amount and the specific account being converted
• Decide how the tax will be paid before submitting the instruction
• Make the withholding election deliberately rather than accepting a default
• Submit the conversion instruction with both accounts already open
• Retain Form 1099-R, the receiving custodian’s reporting, and the Form 8606 filing

Rules that catch people by surprise

Pro-rata treatment is the most misunderstood. When after-tax basis exists in any traditional, SEP, or SIMPLE IRA, a conversion is treated as coming proportionally from pre-tax and after-tax amounts across all of them — you cannot elect to convert only the after-tax portion. This is why the aggregate balance matters even when converting from one account.

Conversions cannot be undone. The ability to reverse a conversion by recharacterizing it was eliminated for conversions, so a conversion completed in a year based on an income estimate that later proves wrong stays in place. That permanence is a reason many people convert in smaller amounts once the year’s income is reasonably clear.

Five-year timing appears twice, and both instances matter. Qualified Roth IRA distributions depend on a five-year period measured from the first year any Roth IRA of yours was funded. Separately, each converted amount carries its own five-year period relevant to the additional tax if it is withdrawn before age 59½. Publication 590-B sets out the ordering rules that determine which dollars come out first.

Effects outside the retirement accounts are often the largest consideration. Because a conversion increases income for the year, it can interact with income-based determinations elsewhere — how Social Security benefits are taxed, income-related adjustments to Medicare premiums, eligibility for income-tied credits, and state income tax. Those thresholds change and depend on your full return, so they are a matter for your tax professional and current official guidance rather than an estimate on a web page.

Factors that belong in the analysis

Rate comparison sits at the center of most conversion analysis: the rate that applies to the income this year against the rate expected to apply when the money would otherwise have been withdrawn. Neither figure is knowable with certainty, which is why the analysis is usually framed as a range rather than a single answer.

Several structural factors carry as much weight as the rate comparison. Whether tax can be paid from outside the retirement accounts, how long the converted amount would stay invested before being needed, how the account fits beneficiary planning, and whether your state taxes the conversion income all shape the outcome. Spreading conversions across years to manage where income lands is a common technique, and it is a planning decision to work through with a professional rather than a rule.

• The marginal rate applying to the conversion income this year
• Expected rates in the years the money would otherwise have been withdrawn
• Whether tax can be paid from funds outside retirement accounts
• Time horizon before the converted amount would be needed
• State income tax treatment of the conversion, including any change in residence
• Interaction with income-based thresholds elsewhere in your return
• Beneficiary and estate considerations, including different rules for inherited accounts

Questions to work through with a tax professional

A short set of questions turns a conversion from a guess into a calculation, and every one of them requires your actual tax situation to answer. Bringing the account figures and your prior-year return to that conversation is what makes it productive.

Nothing on this page substitutes for that conversation. The items below are inputs; the output depends on a complete return, which is information a preparer already has in front of them and a web page does not.

• What is the total of my pre-tax IRA balances, and do I have any after-tax basis?
• How much income can be added this year before crossing a threshold that matters to me?
• Will estimated tax payments be required, and by when?
• Do I have a required minimum distribution that must be taken before converting?
• How does my state treat conversion income?
• Does converting in stages across several years change the result materially?

Sources to verify

• IRS — Rollovers of Retirement Plan and IRA Distributions
• IRS — Rollover Chart (which account types can receive which rollovers)
• IRS — Roth IRAs
• IRS — Traditional and Roth IRAs
• IRS — Publication 590-A, Contributions to IRAs
• IRS — Publication 590-B, Distributions from IRAs
• IRS — Roth Account in Your Retirement Plan
• IRS — Roth Comparison Chart
• IRS — Retirement Topics: Required Minimum Distributions (RMDs)

Educational information only — not tax, legal, or investment advice. Plan rules vary. Advisor availability is confirmed case by case.