This is for Magento 1.4.x - I have discovered that the actual tax rate used for calculation of that order (say 8.25% for example) does not have a field to go into in
sales_flat_order - which is pretty lame IMO considering the number of other detailed pieces of information this table and the _items table have.
I am considering extending the model and adding a
tax_rate field to the table itself. Another option is to extend with an EAV table and store the attribute there. Is the former an acceptable solution, and will it survive an upgrade to version 2.0 which we are planning on doing soon?