User Guide

Instant Payment Notification Manual

Instant Payment Notification

Back-end server-to-server integration

Instant Payment Notification allows you to integrate your PayPal payments with your

website’s back-end operations, so you get immediate notification and authentication of

the PayPal payments you receive.

Note: To activate Instant Payment Notification, you will need to go to your Profile

to enter the URL at which you would like to receive notification posts. For more

information, please refer to the Setting Up IPN section of this document, which

begins on page 13.

How It Works

When a customer makes a payment to you or a payment is reversed or refunded,

PayPal will post a notification to your server at the URL you specified. Included in this

notification will be all of your customer’s payment information (e.g. customer name,

payment amount) as well as a piece of encrypted code. When your server receives a

notification, it will then post the information, including the encrypted code, back to a

secure PayPal URL. PayPal will authenticate the transaction and send confirmation of

its validity back to your server.

After you have activated Instant Payment Notification, your server will be sent a

notification every time you receive a payment. This notification will be sent as a

hidden “FORM POST” to the URL you specified, and will include all of the payment

information. The FORM variables for these notifications are listed in the following table.

IPN Variables

The following variables work for all Send Money, Buy Now, PayPal Donations, and

PayPal Shopping Cart IPNs. If you are using IPN to receive Subscriptions payment

notifications, you will need to support additional variables. Please note that the IPN

variables are case-sensitive. Most values are lower-case, but payment_status is non-

standard with the first letter capitalized (e.g., Completed). For more information on

these additional variables, please refer to the Variables for Each Subscription Type

section of this document, which begins on page 17.

Restrictions on Field Lengths and Data Types

IPN posts contain only alphanumeric characters. The maximum field length for each

returned field is 127 characters, with the exception of the custom field, which has a

maximum length of 255 characters. The unique PayPal Transaction ID will always be

17 characters long.