Problem in Tax amount calculation for Sales Invoice in Trading Division.

We have setup one Trading location in our db. we purchase the material from vendors and sell it to our group companies. both purchase and sales trasactions update the RG 23 d registers.

I have problem in sales document, e.g when i make oa for one item of 60 qty and i want to ship only 10 qty at time of that item the bed amount is calculate automatically using rg 23 d. but the tax amount is calculated wrongly.4118.Untitled.jpg