The Merchant ID is way for PayPal to associate you with your account without exposing your email address to web crawlers and people who want to look at your item button source code. If your are manually coding your own button code, you can use the Merchant ID in place of your account email address as the "business" variable value. This way, you're not sharing your email address with someone if they look at your source code.
If you have a Personal Account, I don't think you will see your Merchant ID via your Profile - things keep changing. Here's a work around.
* Login to your PayPal Account first and remain logged in.
* Next, go to this link. (https://www.paypal.com/us/webapps/mpp/standard-integration)
* Click on "Create Button".
* Just select the Buy Now item button - all you need to do is go through the steps of creating a button, you really won't use the button, you just need to generate one so you can see your Merchant ID.
* On the Button creation screen, just fill in the Item Name and Price.
* Lower on the form you should see the radio button for "Use my secure merchant account ID".
* Next, click on "Create Button".
* On the next screen, you should see your generated button code.
* Click on "Remove code protection".
* You should now see your Merchant ID - it will be the "value" for the "business" variable.
If you have a Business Account:
* Login to your Account.
* Click on "Profile".
* Click on "Profile and settings".
* You should be on the "My business info" screen.
* There you will see your "Merchant account ID
