Transfer of property

Hi, i am selling a plot in dha islamabad for 190 million and the dealer has told me that his client will pay though bank draft for only dc value (37 lac) and the rest will be paid in cash. Furthermore, he is adamant that while transferring the property sale price will be declared in dha as only the dc value (37 lac) not 190 million.
Keeping in view the new ordinance, is it illegal or unwise to contract such deal as now government can buy the same property for double the declared price.

Need urgent advice for a kind hearted fellow