To find the tax exemption related fields while generating invoice for SEZ customer, For this, you need to enable the setting for sales type in that you have to select SEZ sales type, which defaults to BUSY; if not, you have to create SEZ unit sales type. For this, you need to follow the below steps:
Go to the Administration menu.
Select Masters and then Sale Type.
Click on Add to create a new sales type.
Give a name to the sales type.
Choose the region as Central.
Select the SEZ unit as the sales type.
After the above setting, you will find tax exemption related fields for SEZ customer.