The tax calculation for admin order creations is wrong:
The customer group tax class is ignored and default group tax class is
always used.
Index: /app/code/core/Mage/Tax/Model/Calculation.php
===================================================================
--- /app/code/core/Mage/Tax/Model/Calculation.php (revision 127)
+++ /app/code/core/Mage/Tax/Model/Calculation.php (working copy)
@@ -165,7 +165,7 @@
if (is_null($customerTaxClass) && $session->isLoggedIn()) {
$customerTaxClass = $session->getCustomer()-
>getTaxClassId();
- } elseif (($customerTaxClass === false) || !$session-
>isLoggedIn()) {
+ } elseif (($customerTaxClass === false) || (!$session-
>isLoggedIn() && !Mage::app()->getStore()->isAdmin())) {
$defaultCustomerGroup = Mage::getStoreConfig('customer/
create_account/default_group', $store);
$customerTaxClass = Mage::getModel('customer/group')-
>getTaxClassId($defaultCustomerGroup);
}