if you did not specify the lot to be sold even though your default method is SL, you can't use it
The specific-shares method only works if certain conditions are met. The method requires that the investor has purchased multiple lots of the same security at different prices, is selling only some of the investor’s shares in a stock, and has kept a record of the cost basis of each stock or fund purchase.
Assuming all these conditions, the investor must give detailed information to the broker managing the investor’s account on which shares to sell. Otherwise, the average price paid for all shares of the same stock will form the cost basis, and the investor will end up with a greater tax liability than necessary.
