Difference between the two service (and reason) code and class relationship forms
When you define service codes, you can group them into classes for reporting purposes. Two forms let you do this: Service Class and Code Relationship (LP08.3) and Service Code and Class Relationship (LP08.4).
LP08.3 lets you identify the class, and then choose all the codes you want to add to the given class. You might use this after you define a new class, when you want to quickly assign several existing codes to the class. LP08.4 lets you identify the code, then choose all the classes to which you want the code to belong. You might use this after you define a new code, and want to quickly assign the code to several existing classes.
Both forms for defining the relationships are offered just to facilitate data entry when setting these up. The end result is the same.
When you define reason codes and classes you can also group them together the same way. The two forms that are provided for grouping them, Reason Class and Code Relationship (LP09.3) and Reason Code and Class Relationship (LP09.4) are offered for the same purpose as the service code and class relationship forms.