Provisional certificate takes four to six weeks, and the joining date is early July

Our son finished his final semester exams in May and has a job offer that needs a provisional degree certificate on the joining day, in the first week of July. His university's exam office says results will be out by mid-June and the provisional certificate four to six weeks after that. The arithmetic doesn't work. The company's HR says they 'usually accept something', without saying what. Has anyone's child joined with a course-completion letter or a bonafide certificate from the college instead, and was that enough? I teach at a university myself and still can't get a straight answer out of a different one.