A wash sale occurs when you sell an investment at a loss and buy the same investment, or one the IRS considers substantially identical, within 30 days before or after the sale. When that happens, the IRS disallows the immediate tax deduction for the loss. The loss isn’t gone, but its timing changes, and in tax planning, timing can carry real dollars with it.

If you sell an investment for less than you paid, you might reasonably expect to use that loss to reduce your taxable gains or income. The wash sale rule is the condition attached to that benefit, and understanding how it works is the difference between a tax strategy that functions as designed and one that delivers its benefit years later than you planned.

The Wash Sale Rule Explained in Plain Language

To oversimplify slightly: the IRS gives you a tax benefit for realizing a loss, but only if you actually step away from the position. The rule works on what we can call the 61-day window — the 30 days before your sale, the day of the sale itself, and the 30 days after. Buy the same or a substantially identical security anywhere inside that window, and the loss is “washed away” for now.

Instead of disappearing, the disallowed loss is added to the cost basis of the newly purchased holding, which effectively postpones the tax benefit until you sell the replacement security sometime in the future. The mechanics are spelled out in IRS Publication 550, but the intent behind the rule is simple: the IRS wants to prevent investors from claiming a tax loss while maintaining essentially the same investment position. At its core, that makes sense. If you’re going to get a tax benefit, there are rules you must follow.

Taxes and tax rules are normally very complex, but the wash sale rule becomes much easier to understand when you go through a simple example.

Example of a Wash Sale

Consider a hypothetical scenario: you purchased 100 shares of ABC Corp. at $50 per share, so your position is worth $5,000. The stock then drops to $40, and your position is now worth $4,000. You make the decision to sell ABC Corp., which realizes a $1,000 loss that you can use to offset other capital gains or even some of your other income.

• Scenario A – Wash Sale: If you buy back ABC Corp. (or a substantially identical security) within 30 days, the $1,000 loss is disallowed for now. Instead, that $1,000 gets added to the cost basis of the new shares. If you repurchased at $40 per share, your cost basis adjusts back to $50 per share, which is right where you started. If the stock later falls to $30 and you sell again, you’d have a $2,000 loss because of that adjusted basis. The loss you tried to realize earlier wasn’t eliminated, it was just deferred.
• Scenario B – No Wash Sale: If you wait at least 31 days before buying back ABC Corp., the $1,000 loss can be recognized on your taxes in the current year. Nothing else changes because you repurchased ABC Corp. outside the wash sale window.

Wash Sales, RSUs, and Employee Stock Purchase Plans

The investors who trip over this rule are rarely day traders. More often, they’re executives whose compensation delivers company stock on a schedule they don’t control. If you receive RSUs and PSUs, participate in an employee stock purchase plan, or exercise options, shares may be landing in your accounts every month or every quarter, and each arrival can count as a purchase for wash sale purposes.

Here’s where it bites: you sell company shares at a loss, and three weeks later your regular ESPP purchase or a new RSU vest delivers more of the same stock. That automatic acquisition can trigger a wash sale and disallow the loss you thought you had captured, because the wash sale rule doesn’t take into account whether the purchase was intentional. Understanding how RSUs are taxed is the first step, followed by coordinating your sale dates against your vesting and purchase calendar.

Want to hear how wash sales fit into a stock compensation sell strategy? We unpacked it on our investing podcast, Off the Wall. Watch the episode here.

We also touched on selling RSUs and avoiding wash sales on an episode of Between Sips with Emily Harper, CFP® and Jessica Gibbs, CFP®: RSUs: What to Do When They Vest. Stream it on Apple Podcasts or Spotify.

How Direct Indexing and Tax-Loss Harvesting Fit In

Wash sales matter most when you’re actively looking to realize losses through tax-loss harvesting, which can be a major benefit of direct indexing strategies. Because direct indexing lets you own the individual stocks that make up an index (rather than just a mutual fund or ETF that tracks it), there are more opportunities to capture tax losses as each individual position moves up and down.

The dollars involved can be meaningful. Consider a hypothetical scenario: an investor harvests $50,000 of losses across a direct-indexed portfolio in a year when she’s realizing $50,000 of long-term gains from selling a concentrated position. At 2026 federal long-term capital gains rates of 15% or 20%, plus the 3.8% Net Investment Income Tax where it applies (all subject to change), those harvested losses can defer roughly $9,500 to $11,900 in federal tax. However, one careless repurchase inside the 61-day window can disallow part of that benefit and push it into a future tax year — which is why harvesting works best as one part of the broader tax strategies for high-income earners, not as an isolated tactic.

More harvesting opportunities also mean more potential for triggering wash sales if trades aren’t carefully managed. Every client’s trading history and portfolio are unique, so customization is key. Strategies like direct indexing need to be executed with planning and precision, so you can avoid wash sales and stay tax-aware while remaining invested, without drifting away from your intended portfolio allocation.

Benefits of Understanding the Wash Sale Rule

• Consistent Tax Planning: Knowing how the rule works helps you keep the losses you realized and avoid surprises at tax filing time.
• Maintaining Overall Portfolio Strategy: Managing around wash sales creates opportunities to harvest losses thoughtfully while keeping your portfolio aligned with your overall goals. For example, while we might sell ABC Corp., we can purchase shares of a company with a similar risk profile, call it XYZ Corp., to keep comparable market exposure without triggering a wash sale.
• Long-Term Planning: Even if you do incur a wash sale, understanding the rule means your loss is not eliminated but deferred, and you may still capture its tax benefit in the future.

Costs and Trade-Offs of Wash Sales

• Missed Opportunities: Without a tax-aware plan for what to buy next, you might wait 31 days in cash before repurchasing a stock, and during that time the price may rebound, reducing your potential long-term investment gains.
• Inadequate Substitute Investments: Selling a stock and selecting replacement holdings without a plan may avoid wash sales, but it could meaningfully change the risk or return profile of your overall portfolio.
• Added Tax Complexity: Wash sales create basis adjustments that have to be tracked and reported correctly, and misreporting them (even unintentionally) can invite additional IRS scrutiny.

Common Wash Sale Questions

Does the wash sale rule apply to gains? No. The rule only disallows losses. If you sell at a gain and repurchase the next day, the gain is taxable as usual, and no wash sale occurs.

What does “substantially identical” mean? The IRS has not published a precise definition, which is where judgment comes in. The same stock or the same fund clearly qualifies. However, two ETFs tracking the same index may qualify as a wash sale. A different company in the same sector generally does not, which is exactly why swapping into a similar-but-not-identical holding is a common way to stay invested through the window. When the call is close, this is a question for your CPA.

How long do I have to wait to avoid a wash sale? You need to stay out of the security for more than 30 days after the sale (and not have bought it in the 30 days before). Waiting at least 31 days after the sale date keeps the loss intact.

Does the rule apply across my accounts? It can. The IRS has indicated that repurchases in other accounts you control, including IRAs, can trigger the rule, and a repurchase inside an IRA can disallow the loss permanently rather than deferring it. Purchases by a spouse can count as well, so coordination across household accounts is part of doing this correctly.

What to Do Next

The wash sale rule sets the terms for a strategy, but it doesn’t have to stop one. Wash sales won’t erase your tax losses, but they will delay the tax impact and its possible benefits. In the end, the work is understanding timing, trade-offs, and how each decision fits into your broader financial plan, because the more complex your portfolio becomes, the more these details interact.

But let’s be clear: the goal of investing is to make money, not to realize losses. Never let the tax tail wag the investment dog. When markets sell off (and we all know they will at some point), it can be a genuine opportunity to look for tax-loss harvesting trades. At Monument, we believe taxes are one important factor in decision-making, but never the only one. Your allocation, goals, and time horizon should remain at the center.

If you’d like to talk through how wash sales, tax-loss harvesting, and your equity compensation calendar fit together, we offer a complimentary Wealth Check to assess your situation.. Want to start the conversation? Let’s talk.

Note: Monument is neither a law firm nor a certified public accounting firm and no portion of the blog content should be construed as legal or accounting advice. Please consult your CPA for tax advice.

Want to suggest a correction to this article? Email us at info@monumentwm.com. Please note that Monument Wealth Management and its advisors are not tax advisors, and this article is not a replacement for professional legal, accounting or tax advice.