how to get sales tax

Hi,

This is my report.

in this my order quantity is 30 for that total amount is coming and sales tax is also coming for this amount

my query is if my received quantity is 15 total amount is coming but by default the sales tax is coming for 30 order quantity

how can i get sales tax for received quantity…please help me in coding i dont know how to write code

Thanks in advance

R.K.M POWERGEN PVT. LTD.
Goods Receipt Note(GRN)

Suppliers Name

G.R.N. NO.

45646

GRN DATE

22 Apr 2014

AXON

INWARD NO

INWARD DATE

Old No. 124,New No. 18,Virudhunagar,

CH. No

768

CH. Date

22-04-2014

Virudhunagar

LR. No.

8769679769

LR Date

22-04-2014

INVOICE NO

INVOICE DATE

626 125

VEHICLE NO

7877

TINNumber:12345678910

PO No.

RKM-000554

PO Date

22-04-2014

Sl.No

Description

UNIT

INV. Qty

Acpt. Qty

Rate

Amount

Valuation

1

SAN

g

10.00

₹1000000.00

₹100,00,000.00

Total

₹100,00,000.00

Exice Duty

₹0.00

Sales Tax

₹0.00

Freight Charges

Grand Total

₹100,00,000.00

Amount In Words Rs:

Hi friends please help me for the above query.

Thanks in advance.

Ranchoo