Is it permissible to pay a commission to an engineer who helped secure a project, and is there any sin if he lied about his job qualifications? What is the ruling on continuing to pay this commission if the contract is renewed?

The default position is to believe a man's statement that his work in the company has no relation to the selection of contractors. It is permissible to pay him a commission, but the ruling on a commission being a percentage of profit is disputed, with the majority opinion being that it is impermissible.

If he was contracted for a specific commission, the questioner does not have the right to give him less than that amount except with his consent.

As for requesting a continuous commission every time a project is executed, he has no right to it, because it is not in exchange for work from him. He is not entitled to a fee unless there was effort and truthfulness in his reporting, and the inquirer had a purpose in what was reported. It is permissible to give him something as a voluntary donation, out of goodwill.