Date: Erev Shabbos Parshas Vayigash 5564
From: Rabbi Moshe Sofer
To: Unknown recipient
A person pledged a sum to one of several charitable organizations in his city but forgot which one. The Chasam Sofer rules that he should be instructed to pay each organization the full amount, treating the doubt stringently like a forgotten korban pledge, though the court cannot compel him; if he prefers, he may deposit a single payment among all the organizations and withdraw.
Source: Shu"t Chasam Sofer YD §240