How to cater overtaken leave for resign staff

Hi experts,

I have one issue regarding time quota. Currently we grant full quota for all the staff. However, for the staff who will resign, staff should get only earned leave. For example, the full quota for one year is 15 days. Once staff tender resignation, we will re-calculate back the earned leave staff should get. The issue is sometime staff have taken over from the leave he/she should get.

Current solution, we ask HR to delete overtaken leave in infotype 2001 and create to the unpaid leave.I'm wondering how SAP standard cater for this scenario. FYI, we don't use time eval to create leave quota.TQ