-# either or both of these can be used to link cust_bill_pkg to cust_main_county
-my $pkg_tax = "SELECT SUM(amount) as tax_amount, invnum, taxnum, ".
- "cust_bill_pkg_tax_location.pkgnum ".
+# Either or both of these can be used to link cust_bill_pkg to
+# cust_main_county. This one links a taxed line item (billpkgnum) to a tax rate
+# (taxnum), and gives the amount of tax charged on that line item under that
+# rate (as tax_amount).
+my $pkg_tax = "SELECT SUM(amount) as tax_amount, taxnum, ".
+ "taxable_billpkgnum AS billpkgnum ".