Service Purchase Order

Dear Sapiens,

I am creating a purchase order with account assignment catogary "K" and item catogary "D"but when i mentioning the services in service tab of PO i need to put a tax code for each and every service.

now the problem is that it is calculating the tax on line item instead of header level.

for example my total service is of 1000 and service bifurcation is

service A 500

service B 300

service C 200

so service tax should be calculate on 1000 @ 10 % = 100 but it is calculating 300 as i put the tax code for each service.

Please give the valuable input.

Regards,

Umu