The RTS codes file is usually maintained by the dealership.  

To edit an existing one, go to Manufacturer System / 00. Global Data > Standard RTS Code



Enter the RTS Code and company number. Search for it using the ... button. 



When the record is loaded, click Amend. Update the field/s and click Save.



To create a new one, click Insert > New and enter the required information.  Or load an existing one then click Insert > Copy to copy the details and just amend the fields accordingly.   





Enter the RTS Code, Description and other relevant information, then Save.