Can we receive instant notification that a customer has paid online?

Yes. I can integrate any of the major payment systems with your online store so that you will be automatically notified when someone makes a purchase. That notification can take the form of an email message to you, or an update to your website's database. For instance, one client of mine sold electronic greeting cards, and they needed to be made available to the customer immediately after purchase. I used PayPal's IPN to automatically update the database to show that the chosen greeting had been paid for. Another client organizes racing events and wanted to be able to collect online payments from people registering for his races. I integrated iTransact with his race registration page so the user data is saved in a file on his server, so he could download it into his spreadsheet program.