Capital Gain Harvesting vs. Roth Conversions

The retirement tax window — same goal, different tax currency, and how to sequence both.

The retirement tax window. Many retirees enjoy a stretch of unusually low taxable income after wages stop but before Social Security, age-73 RMDs, and persistent Medicare surcharges raise the floor again. That window is finite — use it deliberately or it quietly disappears.

Same goal, different tax currency

Large taxable portfolios with embedded gains and large pre-tax retirement balances both face the same structural question: how to accelerate taxes while brackets are low without overshooting breakpoints that trigger stealth taxes.

Capital gain harvesting

Realize long-term gains in taxable accounts while federal rates on those gains are still favorable — in some years, married filers can use a 0% federal bracket on long-term gains until taxable income crosses the published threshold. Resetting basis now can avoid 15–20% federal rates later. Wash-sale rules do not block immediately repurchasing the same security after a gain harvest the way they can with loss harvesting.

Operates only on taxable brokerage or mutual fund holdings — not IRAs
Still interacts with IRMAA and net investment income thresholds
Best paired with cash needs, basis concentration, or expected future rate hikes on gains

Roth conversions

Shift IRA dollars from pre-tax to Roth by paying ordinary income now. Shrinks future RMDs, builds a tax-free bucket, and can reduce lifetime tax when executed in the same low-bracket years.

Each converted dollar is ordinary income in the year of conversion
Bracket-filling discipline: convert to the top of a target bracket, not through it
Often complements gain harvesting after modeling combined income

How the window closes

Early retirement / gap years — lowest bracket room; both strategies compete for the same space.
Social Security begins — up to 85% of benefits can become taxable; bracket headroom shrinks.
RMD age — forced ordinary income from pre-tax accounts raises the annual baseline; planning flexibility drops.

Four factors that set the mix

Use of funds — near-term spending favors liquidity; legacy goals may favor Roth acceleration.
Marginal stack today — ordinary vs. preferential income ordering changes the next dollar’s tax rate.
Future income picture — pensions, deferred comp, part-time work, and RMD trajectory.
Ripple effects — IRMAA two-year lookback, ACA subsidies if relevant, and state taxes.

When to lean which way

Situation	Lean toward	Why
Large taxable gains; ordinary income still inside 0% LTCG headroom	Gain harvesting	Step up basis at lowest federal gain rates available.
Large IRA; RMDs will dominate future brackets	Roth conversion	Prepay tax now at a known rate; reduce forced income later.
Both large taxable and large IRA; limited window	Blend, sequenced	Model bracket stacking — often Roth to the ordinary cap, then gains.
IRMAA cliff sensitivity	Case-specific	Capital gains still count toward MAGI; neither strategy is “free.”

Common mistake. Picking one strategy by rule of thumb. Most real households need a calibrated blend sized with tax software or professional models — not a single headline recommendation.

Checklist download

Walk through income, accounts, and sequencing questions with our printable checklist.

View capital gain vs. Roth checklist (PDF) Schedule a conversation