Gross price and net price incorrect on PO

Hi Experts:

We have SRM 7.0 and ECC 6.4

Please i create my purchase order with Gross Price 120000 DHS and Net Price 100000 DHs, Cause the TVA VALUE is 20000 Dhs  ( 20%)

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On the item i have a probleme with Gross price and net price, they schould not be the same. I don't anderstand what is the problem.

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Please how can i resolve it?

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Please i need a help

Thanks