Is your company involved in the example as a customer?

Or are both of your clients in the process (not your company)?

Hi, both are customers of ours. One of our Customers purchased another customer of ours. We want to be able to track all the sales product sold for both customers and some have an identifier with each of these two accounts to see the relationship. Is there such a relationship tagging identifier in IFS?

Ok, then it is not a inter company process, right?

And how do you create the customer orders? Manually or via EDI?

​@Cindygcx How do you keep track of the products sold to customer A in your side of IFS?

If these are visible as customer owned stock in your inventory with the customer A name, you could transfer the ownership of your goods to customer B in IFS. 
Since you ask about maintaining a relationship between customers A and B -  What is the nature of this relationship? and going forward for your business? 

We pull sales from the Sales orders by customer in IFS. The question is, is there way to tie to Customers together where the relationship is only from customer B buying Customer A? Would the Hierarchy feature in IFS work to pull sales information from the Hierarchy? 

​@Cindygcx I dont think Customer Hierarchy will help. Is any of the customers defined as a site in your IFS? 
Additionally, you can connect a supplier and a customer in Supplier > Purchase > General section. If that helps. 

Also, I think your scenarios is very specific and also not very clear. 

​@Cindygcx it sounds like you’re selling serial tracked parts.

In such case, it’s possible to use Equipment Objects functionality in Service/Maintenance module.

You could create a Hierarchy of Functional objects. Something like below:

MAIN - root of your hierarchy

      CUSTOMER B - functional object

           SN1234 - serial object sold to customer B

           SN5376 - serial object sold directly to customer B

          CUSTOMER A - functional obj

                SN45456 - serial object sold directly to customer A

                SN65675 - serial object sold directly to customer A

This way, when you get a new customer order, in the line you can specify the Superior Object ID (Customer A or Customer and a serial object will be automatically created inside the Objects hierarchy.

In the end you could end up with a nice looking Hierarchy and you could track warranty at Object level.