Every December, financial advisors send the same email: it is time to harvest your tax losses. They scan the portfolio for positions that are down, sell them before year-end, and book the losses against gains. Then they congratulate themselves on the tax savings. I understand the impulse. But this approach leaves a significant amount of value on the table, and in some cases it creates problems that offset the benefit entirely.
Tax-loss harvesting is not a year-end exercise. It is a discipline that runs every week of the year — or it is mostly theater.
What Tax-Loss Harvesting Actually Is
Tax-loss harvesting is the practice of selling a security that has declined in value to realize a capital loss, then immediately reinvesting the proceeds in a similar (but not substantially identical) security to maintain market exposure. The realized loss can be used to offset capital gains elsewhere in the portfolio — or, if losses exceed gains, up to $3,000 of ordinary income per year, with the remainder carried forward indefinitely.
The mechanics are straightforward. The discipline is not. The reason most advisors do it wrong is that they treat it as a one-time annual event rather than an ongoing process. Markets do not move in one direction. Volatility creates loss-harvesting opportunities throughout the year — in February, in August, in any month when a sector or individual position pulls back. If you only look in December, you are missing most of the opportunities.
The Wash-Sale Rule and Why It Matters
The IRS wash-sale rule disallows a loss if you purchase a "substantially identical" security within 30 days before or after the sale. This is where many advisors create problems for their clients. They sell a position to harvest the loss, then — either through inattention or automatic dividend reinvestment — repurchase the same security within the 30-day window. The loss is disallowed, and the client has incurred transaction costs for nothing.
The solution is to replace the sold position with a similar but not substantially identical security. If you sell the iShares Core S&P 500 ETF (IVV), you can immediately buy the Vanguard S&P 500 ETF (VOO) — both track the same index, but they are issued by different providers and are not considered substantially identical by the IRS. You maintain your market exposure while locking in the loss. After 31 days, you can switch back if you prefer the original holding.
Short-Term vs. Long-Term Losses: The Hierarchy Matters
Not all losses are created equal. Short-term capital losses (on positions held less than one year) offset short-term capital gains first. Long-term losses offset long-term gains first. This matters because short-term gains are taxed at ordinary income rates — as high as 37% — while long-term gains are taxed at preferential rates of 0%, 15%, or 20% depending on income.
The most valuable losses to harvest are short-term losses that can offset short-term gains. A $50,000 short-term loss that offsets a $50,000 short-term gain saves $18,500 in federal tax for someone in the 37% bracket. The same loss offsetting a long-term gain saves only $10,000 at the 20% rate. Understanding this hierarchy is essential to prioritizing which positions to harvest.
The Interaction With Your Broader Tax Picture
Here is where tax-loss harvesting becomes genuinely complex, and where the coordination between your investment advisor and your CPA becomes critical. The value of a harvested loss depends entirely on what you are offsetting it against. If you have no capital gains this year, harvested losses reduce ordinary income by only $3,000 — the rest carries forward. If you are in a low-income year, the tax savings may be minimal. If you are planning to sell a business, the harvested losses could offset millions in capital gains.
This is why we review our clients' full tax picture — not just the investment portfolio — before making harvesting decisions. We want to know: What is your projected income this year? Do you have a liquidity event planned? Are you carrying forward losses from prior years? The answers to these questions determine whether harvesting a particular position is worth the transaction cost and the 30-day reinvestment risk.
What a Year-Round Approach Looks Like
In practice, we monitor client portfolios for harvesting opportunities continuously. When a position declines by a meaningful threshold — typically 5% to 10% from its cost basis — we evaluate whether harvesting makes sense given the client's current tax situation. We track wash-sale windows carefully, coordinate with the client's CPA on projected year-end tax liability, and document every decision.
The result is not a dramatic year-end scramble. It is a steady accumulation of tax alpha — incremental savings that compound over time. For a client with a $2 million taxable portfolio, disciplined year-round harvesting can generate $15,000 to $30,000 in annual tax savings in volatile markets. Over a decade, that is a material difference in after-tax wealth.
If your current advisor sends you a single email in December about tax-loss harvesting, that is a signal worth paying attention to. It means they are treating tax efficiency as an afterthought rather than a core discipline. The question to ask is not "did we harvest losses this year?" — it is "how much tax alpha did we generate, and how does that compare to what was available?"