hey -- thanks for the quick response. the VAT mod does not modify the function_prices.php file. here is a list of files which are added/modified by the VAT mod
Code:2. New files included in package
admin/includes/functions/extra_functions/functions_vatmod.php
admin/includes/languages/english/extra_definitions/vatmod.php
catalog/includes/functions/extra_functions/functions_vatmod.php
catalog/includes/languages/english/extra_definitions/vatmod.php
3. Modified files included in package
admin/customers.php
admin/invoice.php
admin/orders.php
admin/packingslip.php
admin/includes/classes/order.php
admin/includes/functions/functions_customers.php
catalog/includes/classes/order.php
catalog/includes/functions/functions_customers.php
catalog/includes/functions/functions_taxes.php
catalog/includes/modules/checkout_new_address.php
catalog/includes/modules/create_account.php
catalog/includes/modules/order_total/ot_shipping.php
catalog/includes/modules/pages/address_book_process/header_php.php
catalog/includes/modules/pages/address_book_process/jscript_main.php
catalog/includes/modules/pages/checkout_payment_address/jscript_main.php
catalog/includes/modules/pages/checkout_shipping_address/jscript_main.php
catalog/includes/modules/pages/create_account/jscript_form_check.php
catalog/includes/templates/YOUR_TEMPLATE/templates/tpl_modules_address_book_details.php
catalog/includes/templates/YOUR_TEMPLATE/templates/tpl_modules_checkout_new_address.php
catalog/includes/templates/YOUR_TEMPLATE/templates/tpl_modules_create_account.php