Is it permissible for a treasurer to benefit from the price difference between wholesale prices and pro forma invoices when purchasing supplies for which no invoices are issued from wholesale markets?

This transaction is religiously forbidden because it involves taking the institution's money illicitly and through deceptive tricks. The purchasing manager is an agent for the institution, and it is his duty to act in the best interest of his principal by buying at the best prices. He must return the difference to the institution's treasury if he buys at a lower price, and it is not permissible for him to take the difference for himself, based on the Almighty's saying: ﴿And do not consume your property among yourselves through falsehood﴾. This action by the purchasing manager is a betrayal of the trust placed in him, based on the Almighty's saying: ﴿O you who have believed, do not betray Allah and the Messenger or betray your trusts while you know [the consequence]﴾. Therefore, he must repent to Allah and return the money to the institution.