WCT in Karnataka

One of my client is working on contracts of erection of electric fencing etc,he however in turn subcontracting the supply & service of parts.
but as in our case it like that,
1.vendor is raising bill quoating WCT In his invoice,
2.My client while making payament deducting the wct Amount from vendor bill he is payaing to govt in turn issuing WCT certificates to the vendor is it a right way to follow the statuet?
3.vendor is taking the WCT on whole amount without deducting ttarget='_blank' rel='nofollow' hrefrom labour & service charges.