Is it permissible to donate a sum of money on behalf of the manager in case of doubt about its delivery to him, for fear of being questioned by him and affecting the professional relationship?

Donating money on behalf of the manager is not sufficient, as it is possible to deliver it to him. Allah Almighty says: (Indeed, Allah commands you to render trusts to whom they are due). Therefore, you must be forthright with the manager about the uncertainty of delivering the amount and your readiness to deliver it as a precaution. Donating a right on behalf of its owner is only permissible when unable to deliver it to him.