The internal Tax Management in BFS is used for applying transaction based taxes. For example when dividend is received by a customer the securities firm that operates BFS should deduct the correct tax and reserve that amount in order to release the amount to the relevant tax agency.
The actual tax reporting is being done by an add-on application called Tax Manager Application so the internal configurations in BFS for tax is only there in order to manage transaction based tax transfers.
BFS will also manage taxes between various source and destination countries. For example if a UK based securities firm is operating BFS and a UK based end customer receives dividend from a US based company the Cross-Border Tax Rates settings should be used to manage the source tax.