Btw, what tripped me up recently is that I misunderstood the "buy the security back within 30 days" part and was quite confused why my broker was showing me a w

Btw, what tripped me up recently is that I misunderstood the "buy the security back within 30 days" part and was quite confused why my broker was showing me a wash sale: I did something like: * Day 1: Buy 100 shares of Stock A at $100 * Day 2: Buy 100 shares of Stock A at $110 * Day 3: Sell 100 shares of Stock A at $90 (using most recent lot for cost basis) Result: The loss of $10*100 on Day 3 is disallowed because the sale was _within_ 30 days of the last stock purchase. I failed to realize that it would apply to a period of 30 days both before and after a transaction, always thought the only way to trigger a wash sale is with a Buy.