How to Configure Zen Cart for PayPal

Basic Paypal IPN Setup
1. Go to the Instant Payment Notification (IPN) setup page in your PayPal account. First log in to your PayPal account, click on 'Profile' and then the 'Instant Payment Notification' button in the 'Selling Preferences' list. Setting this up ensures that your Zen Cart store and PayPal are synchronized with each other when payments are made.
2. To properly set up IPN service, click on 'Edit IPN Settings' on the setup page. Enter the IPN notification URL and select the radio button for 'Receive IPN messages.' Click the 'Save' button and then on 'Back to Profile Summary' on the next page. The IPN notification URL is found in the top left-hand side of the PayPal IPN's information settings in the payment modules of your Zen Cart administrator area.
3. Set the Auto Return feature to allow customers to automatically return to your Zen Cart store after paying with Paypal. Click on 'Website Payment Preferences' under the 'Selling Preferences' list on your Paypal profile page. Turn Auto Return on by selecting the 'On' radio button. Enter the 'Return URL' in the space provided; this URL is found next to where your IPN notification URL was listed in your Paypal payment module in the Zen Cart admin area. Scroll to the bottom of the Website Payment Preferences page and click 'Save.'
4. Log in to your Zen Cart administrator panel with the username and password that you created when you signed up with Zen Cart.
5. Go to the payment modules in your Zen Cart admin control panel. Click the 'Payment' option under the 'Modules' tab to see a list of all possible payment options for your customers. Click the 'Paypal IPN - Website Payments Standard' payment option and click 'Edit' at the top.
6. Enter the appropriate information in the left-hand-side information box to properly set up PayPal on your site. Confirm that the 'True' radio button is marked to enable the PayPal module. Enter your primary premier or business PayPal email address under the 'Business ID' section. Choose other desired options in this section as well, such as selecting your preferred transaction currency; click 'Update' at the bottom of the page when finished. If you're unsure of your primary PayPal address, this is the email address marked as primary in the 'Email' section on your PayPal profile page.
PayPal Express Checkout Setup
7. Go to the API Access setup page in your PayPal account. First log in to your PayPal account and click on 'API Access' under the 'Account Information' list in your PayPal profile page.
8. Click 'View API Certificate' on the API Access page to view your API credentials. Write down or copy the API username, password, and signature on the next page.
9. Log into your Zen Cart administration and choose the 'Paypal Express Checkout' option in the Payment modules. Select the 'True' radio button to enable this payment option; scroll down and set any other desired settings, such as choosing to allow customers to 'skip' the checkout payment page when making a payment. Paste your API username, password, and signature in the appropriate boxes. Select 'Live' to make the PayPal Express Checkout payment option ready to use. Click 'Update' at the bottom of the page when finished.