Does Swapping Between Similar Funds Avoid the Wash Sale Rule?
Selling a fund at a loss and immediately buying something similar feels like a clean way to keep investment exposure while capturing a tax benefit, but a long-standing rule exists specifically to police how “similar” that replacement is allowed to be.
The short answer
The wash sale rule disallows a tax loss if a “substantially identical” investment is bought within a window around the sale. Swapping into a fund that tracks a different but related benchmark is generally understood to avoid this problem, because the two funds aren’t considered substantially identical securities, even though the rule doesn’t define that term with a precise, mechanical test.
What the wash sale rule is trying to prevent
The rule exists to stop someone from selling an investment purely to realize a tax loss while keeping essentially the same position. If a taxpayer sells shares and buys back the same or a substantially identical investment within the rule’s window, the loss is disallowed for current tax purposes and generally gets added to the cost basis of the replacement shares instead of being usable right away.
Why “substantially identical” is the key phrase
- Two funds tracking the same exact index are generally viewed as more likely to be substantially identical, since their holdings and performance would be nearly indistinguishable — closer to the kind of comparison you’d make between an index and its benchmark than between two genuinely different strategies.
- Two funds tracking different but related indexes — say, a broad market index versus a similar but distinct benchmark — are generally treated as different enough to avoid the substantially identical standard, since the underlying holdings and weightings differ.
- The exact line isn’t spelled out with a bright-line test, which is why this remains a nuanced area rather than a simple checklist, and why generalizations should be treated cautiously.
How this connects to broader fund tax planning
This nuance is part of why some investors use paired funds — tracking similar but not identical benchmarks — specifically for tax-loss harvesting, selling one to realize a loss while buying the other to stay invested in a similar market segment. This differs from specific identification, which is about choosing which existing shares to sell rather than what to buy afterward, but both concepts often come up together in loss-harvesting discussions.
What to weigh
Because the definition of “substantially identical” isn’t a fixed formula and depends on the specific facts of each situation, general education about ETFs and mutual funds swapping between related-but-different benchmarks shouldn’t be read as a guarantee that any particular pair of funds will hold up under scrutiny. Rules in this area are set by tax authorities and can be interpreted differently depending on circumstances, so this is an area where the details of the specific funds involved matter quite a bit.
The bottom line
Swapping between funds that track genuinely different benchmarks is generally treated differently from buying back the same investment, which is why some investors use this approach around tax-loss harvesting. But “substantially identical” is a judgment call rather than a precise rule, which means this is a topic worth understanding carefully rather than assuming any two similar-sounding funds are automatically safe substitutes.