tax exemptions

Dear All,

kindly give your thoughts on

we have a fixed tax in tax_codes_map (i.e no DM for tax) and we have billing time taxation

1) To exempt accounts from tax , all we have to do is just add PIN_FLD_EXEMPTIONS[] array to /account.

2) If no, what else to do?

3) If yes, what are the values to PIN_FLD_EXEMPTIONS[].pin_fld_percent and PIN_FLD_EXEMPTIONS.pin_fld_type ?

4) Can we fill up PIN_FLD_EXEMPTIONS[] during commit_customer opcode or modify_customer ? or is there any exceptions to this ?

4) If we have exempt only a certain type of event like purchase , cycle etc, what is the way ?