Not necessarily. The rules don't say "similar" they say "substantially identical." It isn't clear how they treat two index funds from different issuers (e.g.,

Not necessarily. The rules don't say "similar" they say "substantially identical." It isn't clear how they treat two index funds from different issuers (e.g., Vanguard and Schwab) that track the same index. While the IRS has not issued any guidance to suggest that such two funds are “substantially identical,” a more conservative approach when dealing with an index fund portfolio would be to repurchase a fund whose performance correlates closely with that of the harvested fund, but tracks a different index.