What, you don’t speak Google? Google makes everything as complex as possible, why should this be any different?

So, When setting up your Google Checkout as a payment Gateway for the first time there are several factors that you need to take into account that could cause errors when trying to checkout. These are obstacles that are NOT clearly documented on Google’s website. They’re Google, Why would they?

When using this necessary evil, Please go through the following steps:

1.) Make sure in your Google Checkout account that you are using API version 2.0 or later.

Also in your Google Checkout account make sure you have followed these steps:
In your Google Checkout control panel go to Settings -> Integration and set the following settings:

* Copy and paste this link into the ‘API callback URL’ field in the Google Checkout control panel: https://yourstore.com/modules/checkout/googlecheckout/xml.php
* If you want to capture the customer’s phone number you must enable Return the buyer’s ship-to phone number in the new order notification and Return the buyer’s ship-to phone number in the new order notification
* Make sure that My company will only post digitally signed carts is ticked
* Make sure that the Callback method is set to XML
* Save your Google Checkout integration settings.

Here is what this screen looks like just in case. . .
Google Checkout Settings for Integrating Google Checkout with BigCommerce

2.) Google Checkout requires at least two tax classes, the store comes with 4 classes predefined. If you have deleted these, you will need to recreate at least two under Tools -> Tax Settings.

3.) If using the Default Global shipping zone this will cause Google Checkout to produce errors as there are countries that Google Checkout does not support.

If you need international shipping, you will need to create a separate zone for international and make sure you do not include the following countries:

AD – Andorra
CU – Cuba
IR – Iran, Islamic Republic of
LY – Libyan Arab Jamahiriya
MM – Myanmar
SD – Sudan
SY – Syrian Arab Republic
IM – Isle of Man
JE – Jersey
GG – Guernsey
KP – Korea, Democratic People’s Republic of
RS – Serbia
ME – Montenegro

4.) If setting up shipping for the US, Google Checkout does not support the Armed Forces Bases; you will need to setup US shipping zone by State and select the individual states to which you will ship.
However, if you are setting up Google Checkout for the UK, then the United States needs to be designated using the “By Country” method.

5.) If using the £ symbol on your store you cannot use this in your product name, product description or in your tax or shipping names. This will cause this error “The entity ‘Acirc’ was referenced, but not declared.”

6.) If you set up a Fixed Shipping Cost on the product level this opens up the entire world for shipping at that cost, which in turn will open up the areas Google Checkout does not ship to and will cause errors.