What is the ruling on the profits gained by a salesperson from selling products at a price higher than that set by the company, or keeping gifts (bonuses) allocated for large deals, with the knowledge of the manager?

The preponderant opinion we hold is that this transaction is permissible, and you are entitled to the profit exceeding the price set by the company, based on Ibn Qudamah's statement: "If he said: 'Sell this for ten, and whatever extra is yours,' it is valid, and the excess is his; for Ibn Abbas saw no harm in it."

As for the gift, the basic principle is that it belongs to the buyer. However, if the company is aware and approves of you taking it, then there is no harm upon you.

The default assumption is that the manager is truthful, but if you doubt his honesty, then ask the owner of the company.