Payment Terms-Cash discount-Apply VAT Checkbox

Hello,

Does anyone know what is the Apply VAT Checkbox do in the cash discount?

how to set it up?

It is in the MENA localization and i cannot find any resource to check.

EDIT 1: I cannot add the Cash Discount unless I uncheck that option! and it gives error:VAT correction value must be set to 'No'

The customer has a scenario where he may have VAT on sales discounts and i wanted to check if this option is related.