http://blogandretire.com/blog/2012/02/redirect-buyers-to-your-site-after.html

1. Turn Auto Return On
http://stackoverflow.com/questions/25829476/paypal-auto-redirect-after-successful-payment

**2. Add the Proper Redirect Code to Your PayPal Button Code - See more at: **

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You can see first url. Have some people test and answer. And in StackOverflow some answer.

when you pay money, login or not that have problem. Some people is login paypal, then have redirect, but no login people can’t redirect.