Tax-Loss Harvesting: What It Saves, and What It Doesn’t
Harvesting a loss rarely erases a tax bill — most of the time it moves it. That can still be worth a great deal, but only if you know where the benefit actually comes from.
Every fall, somebody forwards us a version of the same article. The headline is usually "Turn your market losses into tax savings". The article isn't wrong, exactly. It just stops about halfway through the story — and the half it leaves out is the half that decides whether harvesting is worth doing at all.
Here is the part that gets skipped: harvesting a loss usually doesn't erase a tax bill. Most of the time, it moves it.
That's not a reason to skip it. Moving a tax bill is genuinely valuable, and in some situations the bill shrinks rather than simply moves. But you should know which one you're getting before you start selling things in December.
What harvesting actually does
The mechanics are simple. You sell an investment in a taxable account for less than you paid for it. That locks in a realized loss. The loss offsets your realized capital gains for the year, dollar for dollar, with no cap.
If your losses run past your gains, you can use up to $3,000 of the excess against ordinary income — wages, interest, business income — with the rest carrying forward indefinitely to offset future gains or to use against ordinary income in future years.1
Then often times, you would take the proceeds from the sale and reinvest into something similar but not identical, so you're never sitting in cash while the market does whatever it's going to do. That last step is the whole point. Harvesting is a tax move, not a market timing call.
Note that carried-forward losses keep their character. A short-term loss stays short-term when it rolls into next year, and that matters more than most people realize.1
The part that gets left out
When you sell at a loss and buy the replacement, your cost basis resets to the new, lower amount.
Lower basis means a potentially bigger taxable gain later if you sell. You claimed a deduction today and, in exchange, you signed up for a larger gain if you eventually sell the replacement. That's the trade. It isn't free money. It's a deduction now paid for with a gain later.
Here's the thing, though: that trade is often still a very good one. You just have to know why.
When does this make the most sense?
1. The rate spread. This is the big one. Short-term gains and ordinary income are taxed at your regular income tax rate — as high as 37% federally. Long-term gains are taxed at 0%, 15%, or 20%. If you harvest a loss against income taxed at a high rate and pay the bill back later at the long-term rate, the difference is real savings, not just a deferral.
A hypothetical illustration: say you harvest a $30,000 loss and use it against $30,000 of short-term gains taxed at 35%. You save $10,500 this year. Your basis in the replacement drops by $30,000, so when you sell it years later as a long-term holding at 15%, you owe an extra $4,500. Net savings under those assumptions: $6,000 — which is just the $30,000 loss multiplied by the 20-point spread between the two rates.
This example is hypothetical and for illustrative purposes only. It assumes federal rates of 35% and 15%, ignores state income tax and the 3.8% net investment income tax, and assumes the replacement position is sold at a gain in a later year. Your rates and outcome will differ.
The same logic drives the $3,000 ordinary income deduction. It's small, but it comes off income taxed at your top rate, every year, until the carryforward runs out.
One caveat there. Carryforwards last indefinitely during your lifetime, but they don't survive you. Unused losses can be claimed on the final return and then they expire — your estate and your heirs can't use them. Losses are worth using while you're around to use them.
2. Time. In that example, you kept $10,500 invested for years instead of sending it to the IRS. That's an interest-free loan you get to compound. The longer the deferral, the more it's worth.
3. The deferral sometimes never comes due. This is the piece almost nobody mentions. Under current law, a few things can make the deferred gain disappear entirely:
You donate the appreciated shares to charity instead of selling them. You skip the gain and generally deduct the fair market value.
You hold until death. Under current rules, your heirs receive a stepped-up basis and the built-in gain is wiped out. You kept the deduction; nobody ever pays the gain.
You sell in a low-income year. A retiree between paychecks and Social Security may land in the 0% long-term capital gains bracket. The gain comes back at zero.
4. Offsetting a future sale. If you are a business owner preparing for a future exit, or a farmer who will eventually sell land or equipment, you know a massive tax bill is on the horizon. Tax-loss harvesting allows you to actively "bank" these investment losses year after year, carrying them forward indefinitely. When the day comes to sell your business or transition the farm, those accumulated losses act as a powerful shield, directly offsetting the windfall capital gains of your exit. You are essentially using today's market dips to protect tomorrow's life-changing liquidity event.
When one of those is a realistic part of your plan, harvesting stops being a delay and becomes a real reduction. That's a planning question, not a trading question, and it's the reason this is worth talking through with someone who can see your whole picture rather than just your brokerage statement.
Where harvesting does nothing at all
Being honest about the upside means being honest about the rest:
Retirement accounts. There is no harvesting inside an IRA, 401(k), or Roth. Losses in tax-sheltered accounts have no tax value. This only works in taxable brokerage accounts.
If you're already in the 0% LTCG bracket. You can't improve on zero, and burning losses in a low-bracket year wastes them.
Small positions. A few hundred dollars of loss can get eaten by bid-ask spreads, tracking differences, and the hassle of tracking basis for years. Typically, financial advisors and modern custodians have the tools to manage frequent trading and small positions.
When you'll sell soon at the same rate. If you're going to liquidate next year anyway at the same long-term rate, you've mostly just moved paperwork.
State treatment varies. Not every state follows the federal rules on offsetting other income or carrying losses forward.3 Worth checking yours.
The rule that can undo all of it
The wash sale rule disallows your loss if you buy a “substantially identical” security within 30 days before or after the sale.4 That's a 61-day window with the sale in the middle, and it catches people in ways they don't expect:
It applies across all of your accounts, not just the one you sold from — including your IRA. That version is the worst one. In a taxable account, a disallowed loss at least gets added to the cost basis of the replacement shares, so you recover it eventually. The IRS has ruled that no such adjustment is available inside an IRA. The deduction is simply destroyed.
It applies to your spouse's accounts.
Automatic dividend reinvestment counts as a purchase. A dividend that reinvests two weeks after your sale can disallow part of the loss without you touching anything.
“Substantially identical” has never been precisely defined for funds. Swapping between two S&P 500 index funds from different providers is a gray area that a lot of practitioners avoid. Moving to a fund that tracks a genuinely different index is cleaner.
None of this is exotic. It's just detail, and detail is exactly what gets missed when this is done in a hurry.
Why this is an October conversation, not a December one
Most people think about this the week between Christmas and New Year's. That's the worst time to start.
Losses are perishable. A fourth-quarter rally can erase the position you were planning to harvest. What's available in October may not be available in December.
Mutual fund distributions are announced in the fall. Funds publish capital gains distribution estimates in October and November and pay them in December. You can owe real tax on a fund you're down on. Knowing that number early is what lets you plan around it instead of reacting to it.
The 30-day window runs forward into January. Sell on December 22 and you can't buy back until roughly January 21. If you have automatic contributions, a rebalance, or a dividend scheduled in that window, you have a problem you can't fix after the fact.
Everything competes at year-end. Roth conversions, required minimum distributions, qualified charitable distributions, charitable gifts, employer stock decisions, estimated payments. Harvesting interacts with all of them — the losses you use here aren't available over there. Sequencing matters, and there is no time to sequence anything on December 29.
And there's a hard stop. The trade has to be executed by the last trading day of the year to count for that tax year. Some holdings have earlier practical cutoffs.
What this looks like done well
Harvesting is not a December scramble to find red numbers. Done properly, someone is watching your taxable accounts through the year, knows your realized gains to date, knows what your fund distributions are likely to be, knows your bracket and whether it's about to change, and knows whether those shares are eventually going to a donor-advised fund, to your kids, or to a closing table on a house.
That's the difference between capturing a tax deduction and building a tax plan. The mechanics of harvesting are simple enough that anyone can do them. Knowing whether to, and when, and against what — that's the part worth getting right.
If you're holding positions that are down, or you're expecting a large gain this year from a business sale, real estate, or a concentrated stock position, this is the season to look at it. Not the last week of December.
If you would like to implement this strategy or learn more, please reach out.
Notes
Rules described here reflect federal tax law as of the date of publication and are subject to legislative change. This material does not address the treatment of digital assets, which is unsettled and the subject of pending legislation.
This material is for informational purposes only and does not constitute investment, tax, or legal advice. Past performance is not indicative of future results. Please consult a qualified advisor before making financial decisions.
Footnotes
1 IRC §§1211(b) and 1212(b). The $3,000 annual limit against ordinary income is $1,500 for married taxpayers filing separately, and it is not indexed for inflation. Carried-forward losses retain their short-term or long-term character. See IRS Topic No. 409 and Publication 550.
2 Capital loss carryovers are personal to the taxpayer. They may be used on the decedent's final return but do not pass to an estate, to heirs, or — beyond the year of death — to a surviving spouse. Where a joint return is filed for the year of death, carryovers must be traced to the spouse who incurred the loss. See Rev. Rul. 74-175.
3 State treatment of capital losses is not uniform; some states do not permit a net capital loss to offset other income or to be carried forward. Confirm your own state's rules.
4 IRC §1091. Rev. Rul. 2008-5 provides that where an individual sells at a loss and causes his or her IRA or Roth IRA to acquire substantially identical securities within the window, the loss is disallowed and the individual's basis in the IRA is not increased under §1091(d).
