<p>What happens if a university that only accepts 1 letter receives two? Will they toss out the one that came last, or do something else?</p>
<p>it will vary with the school and with whether you’re on the borderline or not. if you prefer one over the other i would write admissions a very polite email apologizing for accidentally sending more than they ask for, and requesting that they look at letter A rather than B if at all possible.</p>