Google Checkout – XML API associate callback serial number with original order

The way I’ve done this in the past is using the <merchanrt-private-data> tag in the original cart, so something like: <checkout-shopping-cart xmlns=”″> <shopping-cart> <merchant-private-data> <merchant-note>[some secret about the cart on my system]</merchant-note> </merchant-private-data> <items> … </items> </shopping-cart> </checkout-shopping-cart> Then, after Google has called back with a serial number, I use the Notification History API to … Read more