Recommendation problem

<p>I want to apply for a top MBA program, and I asked my manager from last year's summer internship to provide a reference. It turned out that the company does not allow any employee to provide recommendation letter. However, I do have a very good performance review from my manager. It's my only professional experience and I recieved an A+ for the job. </p>

<p>Should I submit it as an extra document? Or is this not allowed?</p>