What Counts as Substantially Identical Securities?
What Counts as Substantially Identical Securities?
The wash sale rule disallows losses when you repurchase the "same or substantially identical" security within the 61-day window. Most investors understand the "same" part—selling Apple and buying Apple shares within 61 days is clearly a wash sale. But "substantially identical" is where the rule becomes murky. Is a total stock market index fund substantially identical to a different total stock market index fund? What about bonds with the same maturity? Can you harvest a loss from a dividend-paying stock and immediately buy a non-dividend version? The IRS guidance on this is sparse, which makes it one of the most litigated aspects of wash sale compliance. This article separates clear cases from gray areas, so you can make informed decisions.
Quick definition: "Substantially identical" under wash sale rules generally means securities representing the same property or obligations; the IRS looks at whether they are so similar that selling and repurchasing them achieves no genuine economic change.
Key Takeaways
- The IRS considers securities substantially identical if they represent the same underlying property, making substitution between them economically insignificant.
- Selling a stock and buying the identical stock at any price within the window triggers a wash sale; there is no ambiguity here.
- Mutual funds and ETFs tracking the exact same index are often treated as substantially identical, even if they have different expense ratios or fund families.
- Options on the same underlying stock (calls, puts) and preferred shares of the same company fall into a gray area where facts and circumstances determine the outcome.
- Bonds are substantially identical if they have the same terms; swapping bonds with slightly different maturities or issuers may escape the rule, depending on duration and credit quality.
Clear Cases: Identical Securities
Shares of the same company. If you sell 100 shares of Microsoft and buy 100 shares of Microsoft (or even 50 shares) within the 61-day window, the wash sale rule absolutely applies. The securities are identical, and there is no escape.
The same bond. If you sell a 10-year Treasury bond and repurchase the exact same bond (same issue, same maturity, same CUSIP), a wash sale occurs.
The same mutual fund or ETF. If you sell the Vanguard Total Stock Market Index Fund (ticker VTSAX) and buy the identical fund, a wash sale occurs—even if you buy it in a different account, even if the price is different.
The IRS does not care about price movement, time elapsed, or your intent. If the security is the same, the wash sale rule applies.
Gray Area 1: Different Index Funds Tracking the Same Index
This is where wash sale law becomes genuinely uncertain. Suppose you own the Vanguard Total Stock Market Index Fund (VTSAX) and you sell it at a loss. Can you immediately buy the iShares Core Total U.S. Stock Market ETF (ITOT)? Both funds track the same underlying index—the total U.S. stock market—so your economic exposure is essentially unchanged. Are they "substantially identical"?
The IRS position: The IRS has never published definitive guidance on this specific scenario. However, IRS rulings and private letter rulings suggest that if two index funds track the exact same index and hold substantially the same securities in the same proportions, they may be considered substantially identical.
The practical reality: Most tax professionals and investors assume that different index funds tracking the same index are not substantially identical, particularly if:
- They are from different fund families (Vanguard vs. iShares, for example).
- They have different expense ratios.
- They have different rebalancing schedules.
- They have slightly different holdings (e.g., one includes micro-cap stocks; the other does not).
The logic is that the funds, while similar, are not interchangeable—they are different products with different characteristics. However, this is not a guaranteed safe harbor. If the IRS were to audit you, they might argue that two total stock market index funds are substantially identical because they hold the same underlying property (the total stock market) in materially similar proportions.
Tax professional consensus: To be conservative and avoid audit risk, many advisors recommend waiting 31 days after selling one broad index fund before buying another broad index fund tracking the same index. To harvest a loss immediately and stay diversified, they recommend buying a different index (e.g., sell a total U.S. market fund and buy a total international market fund, achieving diversification while avoiding wash sale risk).
Gray Area 2: Bonds with Different Terms or Issuers
The wash sale rule is generally less aggressive with bonds than with stocks, but it still applies. Here are common bond scenarios:
Same bond, different price: Selling a Treasury bond at a loss and repurchasing the identical bond at a different price within the window is a clear wash sale.
Different maturity, same issuer: If you sell a 10-year IBM bond at a loss and buy a 5-year IBM bond, these are not the same bond. However, they are both IBM debt, and they may be "substantially identical" if the yield curves and credit risks are sufficiently similar. The IRS would likely examine factors such as duration, yield, and seniority. If they are materially different in risk and return, they might escape the rule. If they are practically interchangeable, the rule would apply.
Different issuer, same maturity: If you sell a 10-year corporate bond from Company A at a loss and buy a 10-year corporate bond from Company B, these are clearly different properties (different issuers, different credit risk). A wash sale would be much harder to establish. However, if the bonds are in the same industry, have the same credit rating, and are traded as near-perfect substitutes, the IRS might still argue they are substantially identical in economic effect.
Treasury vs. Municipal bonds: These are different securities with different tax treatment (munis are often tax-exempt; Treasuries are not). A wash sale is highly unlikely if you sell a Treasury bond and buy a municipal bond, even with similar maturity and yield.
Strategy tip: If you want to harvest a loss from a bond and immediately replace it with something similar, swap the issuer or the maturity. This creates a material economic difference and reduces wash sale risk. For example, sell a 10-year corporate bond from Company A and buy a 7-year corporate bond from Company B. The credit risk and duration have changed, making it harder for the IRS to argue the bonds are substantially identical.
Gray Area 3: Preferred Shares and Common Stock
Preferred shares and common stock of the same company are not the same security—they have different terms, rights, and risks. If you sell common stock at a loss and buy preferred shares of the same company (or vice versa), a wash sale is unlikely.
However, if you sell one class of preferred shares and buy another class of preferred shares from the same company, the analysis depends on whether the classes are materially different. If they are economically interchangeable (same dividend, same seniority), they may be substantially identical.
Gray Area 4: Options (Calls and Puts)
This is one of the most litigated areas of wash sale law. If you sell a covered call on your stock position and the option expires worthless, you have not triggered a wash sale (there was no repurchase). But what if you sell a call option to generate income, the option is exercised (your stock is called away), and you immediately buy the stock back? Or what if you own stock, sell a put option below the current price to generate income, and the put is exercised (you are forced to buy more at the strike price)?
IRS guidance: The IRS has issued some rulings suggesting that if you sell a call or put on a security you own (or on the same underlying stock you just sold at a loss), the position may be considered substantially identical to the underlying stock, depending on the strike price, expiration, and other facts.
The practical issue: If you own 100 shares of Stock X, sell a January $50 covered call (with Stock X trading at $55), the call option may be considered substantially identical to the stock. If you sell the stock at a loss and the call expires in-the-money (the stock is called away) or you buy back the call to close it, you could trigger a wash sale.
Common trap: An investor sells shares at a loss, then sells a covered call on those same shares to generate income. The covered call is viewed as a repurchase or continuation of the position, triggering a wash sale on the original loss. Even more treacherous: selling a put option on a stock you recently sold at a loss can trigger a wash sale if the put is exercised and you are forced to buy the stock within the 61-day window.
Strategy: If you harvest a loss on a stock, close out any open calls or puts on that stock during the 61-day window, and avoid initiating new option positions on the same stock until day 31 or later.
The "Substantially Identical" Test: IRS Factors
The IRS uses these factors to determine whether securities are substantially identical:
- Same underlying property: Do the securities represent claims on the same underlying asset or obligation?
- Economic equivalence: Are they economically substitutable? Can you sell one and buy the other with minimal economic change?
- Market perception: Are they traded as interchangeable in the market?
- Risk and return profile: Do they offer the same risk, return, maturity, and credit quality?
If two securities score high on most of these factors, they are substantially identical. If they score low, they are not.
Real-World Example: The Index Fund Swap
You own $50,000 in the Vanguard Total Stock Market Index Fund (VTSAX), which has fallen to $45,000. You sell at a $5,000 loss on November 1. You want to stay fully invested in U.S. stocks but are worried about audit risk if you immediately buy VTSAX again (or another total U.S. market fund).
Your options:
Option A: Wait 31 days and buy VTSAX again. Result: Loss is deductible. Cost: You are out of the market for a month, missing potential gains.
Option B: Buy the iShares Core U.S. Aggregate Bond ETF (AGG). Result: You remain invested, but you have shifted to bonds instead of stocks. Economic exposure has changed materially. Wash sale risk is minimal. Cost: Your portfolio allocation has changed; you are now in bonds instead of stocks.
Option C: Buy the Vanguard Total International Stock Index Fund (VTIAX). Result: You remain invested in equities, but you have shifted to international stocks. Economic exposure has changed (international markets do not move in lockstep with U.S. markets). Wash sale risk is minimal. Cost: Your allocation has changed; you have international exposure instead of U.S. exposure.
Option D: Buy an alternative total U.S. market fund from a different family (e.g., iShares Core Total U.S. Stock Market ETF, ITOT). Result: You remain in the same sector, same index. IRS risk is unclear. Some tax pros accept this; others advise against it. Cost: Uncertain audit risk.
Most conservative tax advisors recommend Option A (wait 31 days) or Option C (buy a materially different index). Option B works if you genuinely wanted to shift to bonds. Option D is a middle ground that most sophisticated investors accept but carries small audit risk.
Common Mistakes
Mistake 1: Assuming index funds are never substantially identical. If you sell the Vanguard Total Stock Market Index Fund and immediately buy the Schwab U.S. Broad Market ETF (which tracks an identical index), the IRS could argue they are substantially identical. Do not assume just because they are from different fund families that you are safe.
Mistake 2: Forgetting about options on the same stock. You sell shares at a loss, thinking you have exited the position, then sell a covered call for income. That covered call might be treated as a repurchase, triggering a wash sale.
Mistake 3: Swapping between very similar bond funds. If you sell a total bond market fund and immediately buy a different total bond market fund, the IRS might argue they are substantially identical, even if from different fund families.
Mistake 4: Not considering sector funds as substantially identical. If you sell a large-cap value stock fund at a loss and buy a different large-cap value stock fund (same sector, same style), the IRS could argue they are substantially identical.
Important Note
The IRS guidance on "substantially identical" is notoriously sparse, and case law is limited. The rule's application to modern products (especially ETFs and sector funds) remains somewhat unsettled. As of the mid-2020s, the IRS continues to issue private letter rulings on edge cases. Before implementing a tax-loss harvesting strategy that relies on selling one fund and immediately buying a similar fund, confirm the current rules with a qualified tax professional or CPA who specializes in securities taxation.
Summary
The wash sale rule applies to substantially identical securities, a term the IRS uses but rarely defines clearly. Identical securities (the same stock, the same bond, the same mutual fund) always trigger the rule. Different index funds tracking the same index, different bonds from the same issuer, and options on the same underlying stock fall into gray areas where facts and circumstances determine the outcome. To be safe, either wait 31 days after a loss sale or swap into a materially different security (different index, different asset class, different issuer). Consult a tax professional for edge cases.