At Scottrade, I can sell any stock in my taxable account, and select the shares that are associated with that trade, AFTER the trade, but BEFORE settlement date.
That’s the policy at almost all brokers because the settlement date restriction is imposed by the tax code itself.
I certainly wouldn’t do business with any broker where tax lots couldn’t be changed ex post facto. There are times when one wants to sell in a hurry and the time it would take to pre-specify the desired tax lots could end up costing serious money.
“The efficient-market hypothesis may be the foremost piece of B.S. ever promulgated in any area of human knowledge!”