Is this Tax included in Basic Rate not working When using on item Quantity

Greetings all. I am having a bit of a problem with Taxes. I need to calculate an inclusive tax based on item quantity. The calculation is done correctly however when I want to make the tax inclusive by selecting the checkbox “Is this Tax included in Basic Rate?” It does not work. The tax is always exclusive of the basic rate. Im not sure what I am doing wrong. Has anyone faced this issue before? What is the solution.?

BTW the ‘Is this Tax included in Basic Rate?’ works when you use On net total