Grafting: How Roth Conversions and Tax-Loss Harvesting Work Together

Most high earners treat Roth conversions and tax-loss harvesting as separate tools. They are not. Used together in the right year, they can meaningfully reduce the tax cost of moving money into a Roth, sometimes to near zero on a portion of the conversion.

The Mechanic: How the Two Tools Interact

Tax-loss harvesting means selling a position in your taxable account at a loss, then immediately buying a similar (but not substantially identical) replacement so you stay invested. The loss gets captured on paper and reported to the IRS.

Those losses first offset any realized capital gains you have in the same year. If losses exceed gains, up to $3,000 of the remaining loss can offset ordinary income each year. Everything left over becomes a capital-loss carryforward, which carries into future years indefinitely.

Here is where the Roth conversion comes in. A Roth conversion is treated as ordinary income. So if you have harvested losses sitting as carryforwards, the $3,000 annual ordinary-income deduction can chip away at the taxable amount of a conversion. It is not a dollar-for-dollar wipeout of the whole conversion, but in the right year, at the right size, it reduces what you owe.

The real opportunity arrives in a down market. When equities fall, you can harvest larger losses. Simultaneously, the assets you plan to convert inside your IRA are also worth less, meaning you convert fewer dollars to move the same number of shares. You get the loss deduction AND you convert at a lower dollar value. Both effects compress your tax bill.

The Rules and Watchouts

A few constraints matter here.

The wash-sale rule (IRC Section 1091) prohibits repurchasing the same or "substantially identical" security within 30 days before or after the sale. Violate it and the loss is disallowed. Buying a different fund in the same asset class is generally fine; buying the same fund back in 31 days is fine. Buying it in your IRA or your spouse's account still triggers the wash-sale rule, a trap many miss.

The $3,000 ordinary-income offset is not $3,000 times your tax rate; it is a $3,000 reduction in taxable income. At a 32% marginal rate, that is $960 of actual tax savings per year from the ordinary-income deduction. The capital-gain offsets, however, can be far larger, because there is no annual cap on using carryforwards against realized gains.

Roth conversions add to your adjusted gross income (AGI) for the year. A large conversion can push you into a higher bracket, trigger Net Investment Income Tax (NIIT) at 3.8% on investment income, or affect your Medicare IRMAA surcharges if you are approaching 63. Size the conversion carefully.

Finally, the replacement asset in your taxable account needs to be something you are willing to hold. Do not harvest into a fund you dislike just to capture the loss.

Worked Example: $50k Conversion in a Down Year

Say it is a year when equities have dropped 20%. You hold $250,000 in a broad index fund in your taxable account with a cost basis of $200,000. After the drop the position is worth $200,000, so you are now at breakeven. But you also hold a $75,000 position in a sector ETF that has fallen to $25,000, giving you $50,000 of unrealized loss.

You sell the sector ETF and immediately buy a different ETF covering a similar (not identical) index. You lock in a $50,000 capital loss.

You have no realized gains this year, so the full $50,000 is available as a loss carryforward. You use $3,000 to offset ordinary income this year per the IRS limit.

You also decide to convert $50,000 from your traditional IRA to your Roth. That $50,000 is added to your taxable income. But you apply the $3,000 ordinary-income offset, bringing the net taxable conversion to $47,000. At a 32% marginal rate, that saves you $960 in taxes this year.

The remaining $47,000 of loss carryforward rolls into next year. Over the following 15 years, you draw down that carryforward against any realized gains in the taxable account, which is where the larger tax-deferral value lives.

The conversion itself, meanwhile, has been moved into your Roth at a depressed value. When markets recover, all of that growth is permanently tax-free.

How This Connects to The Sporos Doctrine

In The Sporos Doctrine: A Life-Centered Framework for Retirement, grafting is the term we use specifically for Roth conversions and tax-loss harvesting because both tools reshape the tax character of assets without changing your economic exposure. This kind of work lives in the Soil layer of the plan, which is the tax architecture built early enough to affect decades of compounding.

The reason we pair these tools deliberately rather than run them in isolation is what the Doctrine calls Tax-Location Alpha: the recognition that a 7% return is not a 7% return if half of it eventually belongs to the IRS. Coordinating the harvest with the conversion in a single down year is one of the cleaner examples of how tax planning and investment management have to be run from the same desk.

Frequently Asked Questions

Can I harvest losses in my IRA to help offset the conversion tax?

No. Tax-loss harvesting only works in taxable accounts. Losses inside an IRA or 401(k) are not deductible and cannot be carried forward.

Is there a limit on how much I can convert in a single year?

There is no IRS dollar cap on Roth conversions. The limit is practical: your marginal rate, IRMAA exposure, and what you can pay in taxes without drawing from the converted funds themselves.

What happens to my carryforward if I do not use it all?

It rolls forward indefinitely. If you die with unused carryforwards, they generally do not transfer to heirs, so using them during your lifetime matters.

Can the loss carryforward offset NIIT as well?

Capital losses reduce your net investment income, which can reduce or eliminate the 3.8% NIIT on investment income. They do not directly offset the NIIT on the Roth conversion amount (which is ordinary income, not investment income).

Does this strategy require a large portfolio to be worthwhile?

You need both meaningful unrealized losses in taxable accounts and a traditional IRA worth converting. That combination is common for HENRYs who have been high earners for a decade or more but have not yet optimized their tax mix.

What to Do Next

1. Pull your current unrealized gain/loss report from your taxable accounts and identify positions that have declined since purchase.
2. Check your existing capital-loss carryforward balance on Schedule D of your most recent tax return.
3. Model what bracket a $25,000 to $75,000 conversion would put you in this year, including IRMAA look-back implications if you are within a decade of Medicare.
4. Coordinate the timing with your advisor before December 31, since both the harvest and the conversion need to settle in the same tax year to work together.

The information provided is for educational purposes only and does not constitute investment, legal, or tax advice. Tax law changes frequently — verify current rules before acting. Consult with qualified professionals for guidance specific to your situation.