Freight separately charged on interstate sale will not form part of sale price, because the definition of sale price under the CST Act specifically excludes freight charged separately.
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[As per sec. 2(h) of The Central Sales Tax Act, 1956, "sale price" means the amount payable to a dealer as consideration for the sale of any goods, less any sum allowed as cash discount according to the practice normally prevailing in the trade, but inclusive of any sum charged for anything done by the dealer in respect of the goods at the time of or before the delivery thereof other than the cost of freight or delivery or the cost of installation in cases where such cost is separately charged.]
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It will be better if you mention the freight charges after the CST amount. For eg.,
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Item xxx
CST xxx
Freight charges xxx
Total xxx
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