Wash Sale Rule

The wash sale rule does not permanently eliminate the disallowed loss — it defers the loss by adding the disallowed amount to the cost basis of the replacement shares, preserving the tax benefit for the future when the replacement shares are ultimately sold in a genuine exit from the position. 

The wash sale rule is directly tested on the Series 65 examination in the context of tax planning, tax-loss harvesting, portfolio management, and the specific circumstances in which the loss is permanently destroyed rather than merely deferred.

The Sixty-One Day Window — The Temporal Framework

The wash sale rule's temporal framework is defined precisely by IRC Section 1091 as the period beginning thirty days before the date of the sale of securities at a loss and ending thirty days after that date — creating a total window of sixty-one calendar days centred on the sale date.

The thirty-day before component is critical and is frequently misunderstood or overlooked — the wash sale rule can be triggered not only by purchases made after the loss sale but also by purchases made before the loss sale within the preceding thirty days. 

An investor who purchases one hundred shares of a stock on November first and then sells one hundred shares of the same stock at a loss on November twentieth — nineteen days after the purchase — has triggered the wash sale rule because the November first purchase falls within the thirty-day window preceding the November twentieth loss sale. This backward-looking component prevents the obvious avoidance strategy of establishing a replacement position before selling the loss position.

The thirty-day after component is the more intuitively understood part of the rule — if an investor sells a security at a loss on December first and then repurchases the same or substantially identical security on December twenty-eighth, the December twenty-eighth purchase falls within the thirty-day window following the loss sale and the loss is disallowed.

Calendar days rather than trading days are the unit of measurement — weekends and holidays count in the thirty-day calculations even though no trading occurs on those days. An investor who sells at a loss on a Friday and repurchases the following Monday has consumed only two calendar days of the thirty-day window — thirty-one calendar days of separation are required between the loss sale and any replacement purchase to avoid the wash sale rule, ensuring that the repurchase falls outside the thirty-day window.

The Substantially Identical Standard — The Definitional Challenge

The most analytically complex aspect of the wash sale rule is the determination of what constitutes a substantially identical security to the one sold at a loss — the standard that triggers the rule even when the repurchased security is not precisely identical to the sold security.

The identical case is straightforward — selling one hundred shares of Apple common stock at a loss and repurchasing one hundred shares of Apple common stock within thirty days is unambiguously a wash sale. The same CUSIP, the same economic instrument, the same issuer, purchased in identical form.

The substantially identical standard is more nuanced and has been the subject of IRS revenue rulings and guidance over decades. The IRS has provided guidance indicating that stock of the same corporation is identical — there is no question about this. Preferred stock of a corporation is generally not substantially identical to common stock of the same corporation unless the preferred stock is convertible into common stock on a one-for-one basis and is subject to no material restrictions on conversion, making it essentially a disguised form of the same common stock.

Bonds of the same issuer with the same coupon rate and maturity date are substantially identical. Bonds with different coupon rates or different maturity dates may not be substantially identical even if they are from the same issuer — the different cash flow streams represent materially different economic instruments.

Options on the same underlying stock can trigger the wash sale rule — purchasing call options on the same stock that was sold at a loss within the thirty-day window can be treated as acquiring substantially identical securities if the options have economic characteristics that make them functional equivalents of the stock itself. An in-the-money call option that is economically equivalent to holding the stock directly may trigger the wash sale rule. Out-of-the-money options that represent a much smaller economic interest than the underlying stock position may not — but this determination depends on the specific facts and the option's relationship to the stock position.

Mutual funds and ETFs tracking the same index present one of the most practically important and most debated substantially identical questions in the context of tax-loss harvesting. Two funds tracking exactly the same index — for example, two S&P 500 index funds from different fund families — are typically considered substantially identical because they represent the same economic exposure through the same basket of securities. An investor who sells the Vanguard S&P 500 ETF at a loss and immediately purchases the iShares S&P 500 ETF has likely triggered the wash sale rule — both funds track the same index, hold the same securities in the same proportions, and produce essentially identical economic outcomes.

However two funds tracking different but related indices — for example, an S&P 500 index fund and a total stock market fund that includes small-cap and mid-cap stocks in addition to the large-cap S&P 500 constituents — may not be substantially identical because the portfolios differ materially in their composition and the economic exposures they provide. The total stock market fund holds thousands of securities not in the S&P 500 and has meaningfully different performance characteristics over time. This is the basis for the most widely used tax-loss harvesting technique — selling a position at a loss and immediately replacing it with a different but related fund to maintain market exposure while potentially avoiding the wash sale rule.

The Basis Adjustment — How the Deferred Loss Is Preserved

The most important practical consequence of the wash sale rule — and the provision that prevents it from being a permanent tax penalty — is the cost basis adjustment applied to the replacement securities when a wash sale is triggered.

When a loss is disallowed under IRC Section 1091, the disallowed loss amount is added to the cost basis of the substantially identical securities that triggered the disallowance — the replacement shares. This basis increase preserves the tax benefit of the disallowed loss by reducing the future taxable gain — or increasing the future capital loss — when the replacement shares are eventually sold.

A concrete example makes the mechanics precise. An investor purchases one hundred shares of a stock at fifty dollars per share — total cost basis ten thousand dollars. The stock declines and the investor sells all one hundred shares at thirty dollars per share — receiving three thousand dollars — realising a three thousand dollar capital loss. Five days after the sale the investor repurchases one hundred shares of the same stock at thirty-two dollars per share — total cost of three thousand two hundred dollars. The wash sale rule is triggered — the three thousand dollar loss is disallowed. However the basis of the newly purchased shares is increased by the disallowed three thousand dollar loss — the three thousand two hundred dollar purchase price plus the three thousand dollar disallowed loss — producing an adjusted cost basis of six thousand two hundred dollars for the replacement shares.

When the replacement shares are eventually sold the investor's gain or loss is calculated from the six thousand two hundred dollar adjusted basis — ensuring that the three thousand dollar loss that was disallowed at the time of the wash sale is ultimately recognised when the replacement position is genuinely exited. If the investor later sells the replacement shares at forty dollars per share — receiving four thousand dollars — the gain is four thousand dollars minus six thousand two hundred dollars, equalling a loss of two thousand two hundred dollars rather than the gain of eight hundred dollars that would be calculated from the three thousand two hundred dollar unadjusted purchase price. The deferred loss has been preserved and will be recognised at the time of the replacement shares' sale.

The Holding Period Tacking Rule

In addition to the basis adjustment, the wash sale rule also transfers the holding period of the sold shares to the replacement shares — a provision called holding period tacking that has important implications for the character of any future gain or loss on the replacement shares.

When a wash sale occurs and the disallowed loss is added to the basis of the replacement shares, the holding period of the replacement shares includes the holding period of the shares that were sold — not just the time elapsed since the replacement shares were purchased. This tacking prevents the investor from resetting the clock on long-term capital gain treatment through a wash sale — if the sold shares had been held for nine months before the wash sale, the replacement shares are treated as if they have already been held for nine months, giving them a nine-month head start toward the twelve-month threshold for long-term capital gain treatment.

This holding period tacking is particularly relevant when the sold shares had been held for less than twelve months — making the disallowed loss short-term — but the investor has previously held the position for a period that when combined with the new holding period would quickly reach the twelve-month long-term threshold.

The IRA Purchase Problem — The Permanent Loss Destruction

The most devastating application of the wash sale rule — and the one most critical for investment advisers to communicate to clients engaged in tax-loss harvesting — is the scenario in which the replacement securities are purchased inside an individual retirement account rather than in a taxable account.

If an investor sells securities at a loss in a taxable brokerage account and within thirty days purchases the same or substantially identical securities in an IRA — whether a traditional IRA or a Roth IRA — the wash sale rule is triggered and the loss is disallowed. However unlike the standard wash sale scenario in which the disallowed loss is added to the cost basis of the replacement shares, the IRS has ruled that when the replacement purchase occurs inside an IRA, the basis adjustment cannot be applied to the IRA account because IRAs do not maintain cost basis in the traditional taxable sense — all growth within a traditional IRA is ultimately taxable as ordinary income regardless of the cost basis of specific positions within the account.

The result is that the disallowed loss is permanently and irreversibly destroyed — it is not deferred to a future sale but is gone completely. The investor receives no tax benefit from the loss in the current year, and receives no future tax benefit through a basis adjustment because the IRA structure prevents the basis adjustment from being carried into the account. This permanent loss destruction from IRA replacement purchases is among the most costly and most commonly encountered tax planning mistakes that investment advisers must help clients avoid.

The Spousal Account and Related Party Extension

IRC Section 1091 and IRS guidance extend the wash sale rule to acquisitions made by the taxpayer's spouse — treating the taxpayer and their spouse as a single unit for wash sale purposes. If one spouse sells securities at a loss in their individual taxable account and the other spouse purchases substantially identical securities in their own individual account within the thirty-day window, the wash sale rule is triggered for the selling spouse.

This spousal extension prevents the obvious avoidance strategy of coordinating simultaneous loss harvesting and replacement purchases between spouses' separate accounts. Joint brokerage accounts, of course, also trigger the rule regardless of spousal considerations.

Corporations and other entities controlled by the taxpayer are also subject to attribution — a taxpayer who sells securities at a loss in their personal account and causes a corporation they control to purchase substantially identical securities within the thirty-day window has triggered the wash sale rule under the controlled entity attribution principles.

Cryptocurrency and the Current Exclusion

As of the 2026 tax year, the wash sale rule has not been extended to cryptocurrency and most digital assets. Internal Revenue Code Section 1091 applies to stock or securities — a definition that has not been amended by Congress to include cryptocurrency tokens, which the IRS treats as property rather than securities for most federal tax purposes.

This exclusion means that as of 2026 investors can sell Bitcoin, Ethereum, or other cryptocurrency tokens at a loss, immediately repurchase the identical cryptocurrency, and claim the full capital loss deduction without triggering the wash sale rule. This tax treatment advantage over traditional securities is frequently cited in discussions of cryptocurrency portfolio management and tax-loss harvesting.

Congress has repeatedly introduced legislation that would bring cryptocurrency under the wash sale rule — treating digital assets as securities for this purpose — but as of the date of this writing no such legislation has been enacted. Investment advisers who work with clients holding cryptocurrency should remain current on any legislative developments that might change this treatment.

Tax-Loss Harvesting and the Wash Sale Rule — The Practical Application

Tax-loss harvesting — the deliberate realisation of capital losses in a taxable portfolio to offset capital gains or reduce ordinary income — is one of the most valuable tax planning strategies available to investment advisers, and the wash sale rule is the primary constraint that must be carefully navigated when implementing it.

The standard tax-loss harvesting protocol involves three steps. First, identify positions in the taxable portfolio that have declined below their cost basis — positions with unrealised losses. Second, sell those positions to realise the losses as deductible capital losses that can offset capital gains or — up to three thousand dollars annually — ordinary income. Third, immediately replace the sold positions with similar but not substantially identical securities to maintain approximately the same market exposure during the thirty-day wash sale window before repurchasing the original securities.

The third step is the critical tax-loss harvesting skill — finding replacement securities that maintain sufficient portfolio exposure to the intended asset class or sector without being substantially identical to the sold security. Common replacement strategies include swapping one S&P 500 index ETF for a total market ETF tracking a different index, swapping one large-cap growth fund for a different large-cap growth fund with different underlying holdings, or swapping a sector ETF for a more broadly diversified fund with heavy exposure to the same sector.

After the thirty-day window has elapsed, the investor may sell the replacement security and repurchase the original security — restoring the original portfolio composition while having successfully harvested the tax loss. This round-trip tax-loss harvesting — sell the original at a loss, hold the replacement for thirty-one or more days, sell the replacement and buy back the original — is the foundational protocol for systematic tax-loss harvesting programmes used by many investment advisers and robo-advisors.

Examination Relevance and Key Takeaways

The wash sale rule is tested on the Series 65 examination in the context of tax planning, tax-loss harvesting, portfolio management, and the specific basis adjustment and holding period tacking consequences of a wash sale.

The key points to retain are these.

The wash sale rule — codified in IRC Section 1091 — disallows a capital loss deduction when the taxpayer purchases the same or substantially identical stock or securities within the sixty-one day window spanning thirty calendar days before the loss sale, the sale date, and thirty calendar days after the loss sale. The rule applies only to loss transactions — sales producing gains are not affected. Calendar days — not trading days — govern the thirty-day calculation.

The disallowed loss is not permanently lost in most cases — it is added to the cost basis of the replacement securities, preserving the tax benefit for when the replacement securities are ultimately sold. The holding period of the sold shares is tacked onto the holding period of the replacement shares, preventing the investor from resetting the clock on long-term capital gain treatment. The substantially identical standard extends beyond exact same securities — funds tracking the same index are typically substantially identical while funds tracking different but related indices may not be.

The most dangerous wash sale scenario is replacement purchases inside an IRA — when the replacement securities are purchased in a traditional or Roth IRA rather than a taxable account, the disallowed loss is permanently and irreversibly destroyed because the IRA basis adjustment cannot preserve the tax benefit — this is among the most costly tax planning mistakes that investment advisers must help clients avoid. The spousal extension treats married couples as a unit — purchases by one spouse within the thirty-day window trigger the wash sale rule for the other spouse's loss sale. Cryptocurrency is not currently subject to the wash sale rule as of 2026 — IRC Section 1091 applies to stock or securities and has not been amended to include digital assets, though proposed legislation could change this status.