Tax-Loss Harvesting and Roth Conversions: Coordinating Two Powerful Strategies

Both tax-loss harvesting and Roth conversions are most valuable when markets are down. Many pre-retirees run both strategies simultaneously — but they interact in ways that surprise people. Specifically: harvested capital losses do not directly offset Roth conversion income. But that doesn't mean they're unrelated. Understanding how the two strategies work together (and where the wash sale rule creates a coordination problem) lets you deploy both more deliberately.

The misconception: capital losses don't directly reduce your Roth conversion tax

The most common misunderstanding: "I harvested $40,000 in losses this year, so my Roth conversion tax will be $40,000 lower." It won't.

Here's why. Roth conversion income is ordinary income — the same tax character as wages or pension payments. Capital losses, on the other hand, are losses from the sale of investment assets. The two live in different parts of the tax code and cannot directly offset each other.

Capital losses first offset capital gains dollar-for-dollar. If you have more losses than gains in a given year, the excess carries forward to future tax years. The only "ordinary income" benefit from a net capital loss is limited to $3,000 per year — a statutory maximum in IRC § 1211(b) that has not changed in decades and is not indexed for inflation.

How the two strategies genuinely work together

Despite the above, tax-loss harvesting and Roth conversions are highly complementary — just not in the way people expect. Four real connections:

1. Both are optimal in the same market conditions

TLH requires unrealized losses to harvest. Roth conversion benefits from depressed asset values (you pay tax on the current price, not the recovery). In a down market, both strategies are simultaneously at their most valuable. Executing both in the same year — rather than waiting for a "better time" — captures maximum opportunity from the same market dislocation.

2. Harvested losses build a future capital-gains shelter

Capital loss carryforwards are a form of tax capital you can deploy in future years. In the years after a Roth conversion — when your IRA balance is shrinking and your bracket room is still available — you may want to realize capital gains from your taxable account (gain harvesting, particularly the 0% LTCG rate for MFJ couples with taxable income below $98,900 in 2026). Losses harvested today offset those future gains dollar-for-dollar. This extends the lifetime tax efficiency of the two strategies combined.

3. The $3,000 deduction creates a small IRMAA benefit

Capital losses reduce your AGI (and therefore MAGI) by up to $3,000/year when you have no offsetting capital gains. For IRMAA purposes, every dollar of MAGI reduction is worth something. If you're managing conversions to stay just under the $218,000 MFJ Tier 1 threshold in 2026, a $3,000 reduction in MAGI from a net capital loss creates $3,000 of additional Roth conversion room.¹ Small — but real.

4. Both free up your taxable portfolio for the future

Harvesting losses resets your cost basis in the taxable account (you buy back a similar-but-not-identical position at the lower price). Over the following recovery, those gains accumulate in an account where you have loss carryforwards to offset them. Meanwhile, the Roth conversion shifts your highest-appreciation assets into an account where they'll never be taxed again. Together, you're systematically reducing the future tax drag on both buckets.

The wash sale rule: where coordination matters most

The wash sale rule (IRC § 1091) disallows a capital loss if you buy a "substantially identical" security within 30 days before or after the sale that created the loss. The key coordination point: IRA purchases count under the wash sale rule.

Per IRS Notice 2008-5, if you sell a security at a loss in your taxable account and purchase the same security in any IRA (traditional, Roth, inherited, or SEP) within the 30-day window before or after, the loss is disallowed — and unlike in a taxable account, the disallowed loss cannot be added to your IRA's basis (it disappears permanently).²

The Roth conversion connection: if your traditional IRA holds the same security you just sold at a loss in your taxable account, converting that position within the wash sale window could constitute a "purchase" of that security in the Roth IRA — triggering the wash sale. The mechanics are debated, but the risk is real enough that practitioners recommend:

• When harvesting a loss in taxable, buy a similar but not identical replacement (e.g., sell one S&P 500 ETF, buy a different one tracking the same index).
• If your traditional IRA holds the same security you sold at a loss, wait 31 days before converting that position.
• Or convert a different position in the IRA that doesn't overlap with your harvested loss security.

In practice, if you hold diverse positions across taxable and IRA accounts, this is easy to manage. The risk concentrates when your IRA and taxable account hold identical ETFs or individual stocks.

Worked example: Susan and David, ages 65/63

Situation: Susan (65) and David (63) are retired. They have $2.1M in a traditional IRA and $680K in a taxable brokerage account. Income: $50,000/year from a FERS pension. IRMAA Tier 1 ceiling: $218,000 MAGI for MFJ. They're planning annual conversions to fill up to the Tier 1 line.

In a down-market year (market falls 22%):

• The taxable account holds a domestic equity fund (purchased at $180K, now worth $132K) — an unrealized loss of $48,000.
• The traditional IRA is down in lockstep — which actually helps, because they can convert more shares at the depressed price for the same dollar amount.

Their strategy for the year:

1. TLH first: Sell the equity fund in taxable, realizing the $48,000 loss. Immediately reinvest proceeds in a different fund tracking a similar (not identical) index. Wash sale rule: avoided.
2. Roth conversion: With $50,000 pension income, their IRMAA ceiling gives them room for $168,000 in conversions ($218K − $50K). They convert $168,000 from the traditional IRA — choosing the same domestic equity position (which has also declined) to maximize shares moved into Roth at the trough price.
3. Year-end MAGI: Pension $50K + conversion $168K − $3K (capital loss against ordinary income) = $215K MAGI. Just under Tier 1 with $3K to spare.

Tax impact of the TLH:

• $3,000 of the $48,000 loss offsets ordinary income → reduces their conversion tax bill by $660 (at 22%).
• $45,000 carries forward for future years.

Two years later (recovery year):

Susan and David want to do some gain harvesting — selling appreciated securities from taxable at the 0% LTCG rate (their taxable income, net of standard deduction and conversion, keeps them in the 0% capital gains zone in some years). The $45,000 carryforward offsets those gains dollar-for-dollar, potentially eliminating capital gains taxes on significant portfolio rebalancing.

The combined result: The Roth conversion locked in the trough price for $168,000 of IRA assets. The TLH created a $45,000 carryforward that shelters future gains. Neither strategy would have worked as well deployed independently or in a different year.

Multi-year coordination calendar

When to prioritize one strategy over the other

Prioritize Roth conversion when:

• You're in the golden window (retirement to RMD age) and each year of delay shrinks the available runway
• Your estate-planning rationale for conversion is strong (large traditional IRA that heirs will inherit in high brackets)
• The market is down and the conversion "discount" is significant
• You have outside funds to pay the conversion tax (not selling from the IRA itself)

Prioritize TLH when:

• You have large unrealized losses in taxable and expect capital gains realizations in the next 3–5 years (portfolio rebalancing, sale of property, LTCG harvesting)
• Your Roth conversion room is already consumed by pension income, Social Security, or required minimum distributions
• You're in a year with an unusually large one-time income event that makes conversion expensive — TLH at least offsets some of that

When there's no tradeoff — do both:

In most years, TLH and Roth conversion don't actually compete. The capital loss carryforward builds up in the background; the conversions proceed to the IRMAA ceiling. The only time there's a genuine tradeoff is if generating the conversion creates a MAGI level where harvested losses would otherwise have kept you under a threshold (IRMAA or SS torpedo). In that case, the loss creates valuable headroom — and you should count it before sizing the conversion.

Frequently asked questions

If I harvest $50,000 in losses, does my Roth conversion become $50,000 cheaper?

No. The $50,000 loss will first offset any capital gains you realize. If you have no capital gains, $3,000 of it offsets ordinary income (saving roughly $660–$1,320 in tax at 22–44% marginal rates). The remaining $47,000 carries forward. Your conversion is taxed at its full ordinary income rate; only the $3K deduction touches that bill.

Can I harvest losses and then immediately convert those same shares to Roth?

You cannot harvest a loss in your taxable account on a security and then convert that same security from your IRA within 30 days — that could trigger a wash sale. But if you're selling one security in taxable at a loss, you can typically convert a different security from the IRA in the same window without issue. Keep the positions separate.

Does tax-loss harvesting affect my IRMAA calculation?

Only by $3,000/year at most. IRMAA uses modified AGI (MAGI) from two years prior. A net capital loss reduces MAGI by up to $3K/year, which creates a small amount of additional conversion room under the IRMAA threshold. For most people, this is a helpful but not transformative benefit.

Should I harvest losses in my IRA?

No — IRA accounts don't generate taxable losses. All appreciation and income inside an IRA is pre-tax; selling at a loss inside the IRA just lowers your account value. TLH only works in taxable brokerage accounts where the gain/loss has tax basis. This is also one reason why keeping some of your retirement assets in a taxable account makes tax planning more flexible.

What securities are "substantially identical" under the wash sale rule?

The IRS is strict about individual stocks (selling AAPL and buying AAPL in an IRA = wash sale) and looser about funds. Selling one S&P 500 index ETF (e.g., IVV) and buying a different one tracking the same index (e.g., VOO) is generally treated as not substantially identical — preserving the loss while maintaining market exposure. Selling and buying the exact same fund is a wash sale. This applies across all accounts.

1. IRS Rev. Proc. 2025-32 — 2026 IRMAA thresholds, tax brackets, and LTCG rates. IRMAA Tier 1: $218,000 MFJ / $109,000 single. 0% LTCG ceiling: $98,900 MFJ taxable income.
2. IRS Notice 2008-5 — IRA purchases trigger wash sale rule; disallowed loss cannot be added to IRA basis.
3. IRS Publication 550 — Investment Income and Expenses — wash sale rule mechanics, capital loss carryforward rules, $3,000 ordinary income deduction (IRC § 1211(b)).
4. Kitces — Wash Sale Rules and IRAs — practitioner analysis of wash sale rule interaction with IRA accounts and substantially identical securities.

Tax values verified as of June 2026. IRC § 1211(b) $3,000 annual capital loss deduction against ordinary income is statutory and not inflation-indexed.