Advanced Features Guide

Table Of Contents
Express Checkout Advanced Features Guide April 2012 83
Implementing the Instant Update API
Following Instant Update API Best Practices
7
NOTE: If the buyer changes their shipping address on the PayPal pages during checkout,
PayPal will make subsequent requests to the callback server.
6. Your callback server responds with the shipping option rates (shown by the red up arrow)
based on the buyers shipping address. You can also adjust the tax amount and send
insurance options. Depending on your business processes, you may send an API call to
your carrier to calculate the rates and options based on the shipping address.
7. PayPal updates the cart review area and Review your information page content to show the
options and rates based on your response.
8. The buyer makes final selections and clicks Continue.
9. You must call GetExpressCheckoutDetails to obtain the buyer’s final shipping option
selections.
10. You call DoExpressCheckoutPayment to perform the transaction.
Following Instant Update API Best Practices
PayPal recommends its list of best practices as a checklist for completing your implementation
of the Instant Update API.
Meet the prerequisites – Provide order line-item details to take advantage of the Instant
Update API.
Streamline the checkout flow – Existing partners and merchants with Express Checkout
integrations can eliminate the current shipping options page.
Use the default callback timeout – Use the recommended 3-second callback response
timeout.
Follow PayPal-defined semantics and syntax – Adhere to well-formed variable names
and syntax rules in the callback response to PayPal. If errors occur in the response, PayPal
uses the flat-rate shipping options.
Call GetExpressCheckoutDetails – You must call GetExpressCheckoutDetails to
find out what options the buyer selected.
Ensure a consistent and good buyer experience – With flat-rate shipping options, you
should honor the rates to ensure a consistent and correct buyer experience.
Localize shipping options – Return localized shipping options, based on the buyers
country and locale, which PayPal sends in the callback request.
Related information:
"PayPal Review Page Order Details" on page 9