Setting up a cashed out annual leave payroll item with correct tax

Hi all, 

I need to set up a cashed out annual leave payroll item , as the tax is generally higher, do I select a specific tax tracking type? It will be under gross payments and I can insert the hours to deduct from annual leave balance. I also know how to manually reduce hours against employee profile. The main thing I want is to set it up so the tax is correct, is this possible or will we need to manually calculate it each time?