Tax-loss-harvesting partner finder

Tax-loss harvesting sells a position at a loss to realize the tax deduction, then immediately re-establishes the same exposure via a different security so the portfolio's allocation barely moves. The IRS wash-sale rule (§1091) disallows the loss if you buy a "substantially identical" security within 30 days before or after the sale.

"Substantially identical" is not statutorily defined for funds. The IRS has not formally ruled on ETF-to-ETF swaps, so no convention is guaranteed to hold up. The convention this site uses — the same one the Bogleheads wiki describes — is:

• Different index (e.g. Morningstar US Total Market ↔ S&P Total Market) is the conventional Bogleheads-wiki swap — not an IRS-issued safe harbor. No letter ruling or court case has tested this convention for ETFs.
• Same index (IVV ↔ VOO ↔ SPYM all track S&P 500) is conventionally treated as wash-sale risk — same securities, same weights, just different wrappers.

Overlap % is the sum of min(weight_a, weight_b) across every security held in both funds — "what fraction of your dollar exposure stays the same after the swap." High overlap means the swap holds your allocation steady; very low overlap means the replacement fund is a different bet, not a TLH partner.

Bps difference shows how much more (or less) the replacement charges. Even "permanent" TLH partners come with a small cost difference; factor that into the savings if you don't plan to swap back.

This tool flags wash-sale risk on benchmark match. It does not constitute tax advice — confirm any harvest with your own CPA, especially across multiple accounts (the wash-sale rule applies portfolio-wide, including spouse + IRA).