To add Adjustment Reason Codes go to Advanced Setup-> Claim Lookups.

On the Search Claim Lookups screen, click on the  button to add a new Claim Lookups.

A new claim lookup window opens up for configuring adjustment reason codes.

Enter the Type by selecting  and choosing ‘Adjustment_Reason_Code’ from the list.

Enter the new reason into the fields named – Code, Code Description, Value, and Value Description.

Keep the User Editable field checked, if the value needs to be edited later.

Hit the  button to add the lookup value.