alter table quote_letter_items add taxable tinyint(3) unsigned not null default 0 after cost;

update quote_letter_items set taxable = 1;

alter table quote_letters change proofing_tax_cost proofing_taxable tinyint(3) unsigned not null default 0;
alter table quote_letters change vendor_in_shipping_tax_cost vendor_in_shipping_taxable tinyint(3) unsigned not null default 0;
alter table quote_letters change shipping_tax_cost shipping_taxable tinyint(3) unsigned not null default 0;
alter table quote_letters change fulfillment_tax_cost fulfillment_taxable tinyint(3) unsigned not null default 0;

alter table quote_letters add taxable_amount decimal(9, 2) unsigned not null default 0 after subtotal;
alter table quote_letters drop item_tax_cost;

update quote_letters
set fulfillment_taxable = 1, 
shipping_taxable = 1, 
proofing_taxable = 1, 
vendor_in_shipping_taxable = 1;