What is the issue with the customer ID? Will you explain what you mean by "ghost" ID?

.  I had previously set up a couple of customers id’s for invoicing that weren’t there on the old backup.  When I try to go in and invoice off those customer id’s now, they aren’t listed in the customer list.  However, when I try to either add them back in or invoice it tells me “the customer ID that was automatically created already exists in Sage 50. Manually enter another customer ID.”  That customer ID that Sage created behind the scenes is not accessible to update or change, can't even find it.

First thing I would do is show the inactive customers. That is where I usually find existing customers that are not in my list. You can activate them and update as needed.

thanks.  I have checked thru inactive customers, but it isn't there.  the error is around a customer "number" that is automatically created when you set up a new customer ID.  However, this number is not shown anywhere nor can you get into it to change it.  when we had to restore to a previous backup due to an error this number/customer id hadn't existed as of the date of backup so I didn't think it would be an issue.  I guess I should have deleted that customer first, then restored to the backup then created the customer again.  now when I go into create a new customer, the system thinks that customer id (the number Sage created behind the scenes) already exists and won't let me create a new one.  I don't know how to "get by" that number behind the scenes.

Ok, so it is something other than the Customer ID that has an issue. I don't have experience with that happening. Sorry I can't be of more help.

thanks for trying!

Have you tried changing the ID?

So go to Options > Global > General tab  

Uncheck the box I highlighted below!

I believe this will resolve your issue.