@SLYKTAX let me try this (and I appreciate this was a post from two weeks ago)
as stated, when you sell a stock, you must declare then and there which lot you are selling. Doesn't matter if FIFO, LIFO or a specific lot, but you must declare then and there and there is no changing that lot later.
For future sales, you can always change the methodology of the remaining lots.
Frankly, to me, the lot to sell is the one with the highest cost basis as it reduces the capital gains tax / increases the loss harvesting. Simply whatever lot has the highest cost per share is the one to sell.
