PayPal Standard has now provided a method, which we now support, to auto-update an order's Shipping/Tax amounts during checkout if the location in the buyer's PayPal profile or the shipping address they provide does not match the location the buyer had specified in their cart. This replicates the behavior that PayPal Pro Express Checkouts have already had for some time.
Previously, there was no way to catch a location mismatch during PayPal Standard checkouts, so we could only catch the mismatch after the buyer had already completed checkout, when PayPal sent our system the IPN confirming completed payment. In that case, we would not have processed the sale and instead would have sent you a notification email reporting the mismatch, so you could decide how to handle the situation yourself.
Now with this latest update, if the buyer gives a country/postal code in their cart, with Shipping/Tax calculated in the cart accordingly, and then proceeds to a PayPal Standard checkout where they provide a different location or shipping address, PayPal's checkout system will catch the mismatch and communicate back our Shipping and Tax calculator to automatically recalculate the Shipping/Tax amount right there during checkout.
This new feature should operate seamlessly for all users and requires no special attention on your part to take advantage of, but please let us know if you encounter any strange issues with Shipping/Tax recalculation during PayPal Standard checkouts.
