Note: To ensure a systematic approach, the application of unused credits will follow the order of excess payments first, then credit notes, and finally retainer payments.

Workflow Rule: 

Go to Settings -> Automation -> Workflow Rules -> +New Workflow Rule and set up the workflow rule as shown below:-

In the final step of this workflow rule, associate the custom function you created and then hit Save.

With this function in place, you no longer need to apply the unused credits manually. Instead, the system will identify any available credits and automatically apply them after you create an invoice. 

If you need any assistance with setting up the function, do not hesitate to reach out to us at support[at]zohobooks[dot]com.

Regards,
Shireen Farhana S