The default tax basis arrangement for all accounts is First In, First Out (FIFO), but it can be changed on a per day and per symbol basis. To change the default matching method for your account, login to the Client Portal version of the Tax Optimizer. Your change will be effective instantly, and will apply until you choose to change it again. If you accept to change the "Method for All" in the TWS version or "Today's Match Method" in the Client Gateway version, the change applies only for the specified trading day and your account will go back to using the default match method the following trading day. In addition, you can select to apply the "Method for All" or "Today's Match Method" to a certain symbol. This change applies  only for the specified trading day and your account will go back to using the default match method the following trading day.