You can assign a permanent reason code to a general journal template. Then the reason code will appear on all entries posted in batches using the template.
Open the 
General Journal
Templates window.
On the line with the selected journal template, click the
Reason Code field, and then
click the AssistButton 
to see the reason codes.
Select the desired code, and then click OK.
Close the journal template.
The selected reason code will be copied to new journal batches created under this journal template. You assign reason codes to journal templates in the other application areas in the same way.
Assigning Reason Codes to Journal Batches
Assigning Reason Codes to Journal Lines
Using Reason Codes when Invoicing