Reb Naftali Weinberg in his Rav Chaim Kanievsky on Shidduchim had posed a queestion to Maran Sar HaTorah about whether one may ask a Shadchan to return the shadchanus if the engagement was broken. Rav Chaim zatzal ruled that one may not.
Broken engagements are never a pleasant item of discussion, and there are often stories about various repercussions of someone who is still angry about the cancellation of the nuptials. On account of this, it is the custom in Israel for both parties to sign documents of mutual forgiveness.
When dealing with dating someone with a broken engagement, there is no question that one should investigate the reason completely, and make sure that a Shtar Mechila, (a document that states both parties completely forgive each other) was both received and given by both parties. This was the custom in all of Poland and in many other countries as well (See Sridei Aish Vol. I #91). The Responsa Sefer Dvar Yehoshua CM Vol. III #5 writes that oral forgiveness does not work – it requires either two witnesses or a written document.
Rav Henoch Leibowitz zatzal, the Rosh Yeshiva of Yeshiva Chofetz Chaim was very strict on this matter too. Rav Moshe Feinstein zatzal (Even HoAizer Vol. IV #85) writes regarding a case of a broken engagement that a Shtar Mechila is necessary. It should be noted that a Cherem was placed upon a person who breaks a Shidduch, that is why it is such a serious issue. Most poskim hold that merely receiving oral forgiveness is not sufficient (Dvar Yehoshua Vol, III CM #5). Some require a full Bais Din saying Machul lach, Machul Lach, Machul Lach – three times.
The Vilna Gaon wrote that it is preferable to get married and then divorced rather than break up a Shidduch (if it had tnaim). This does not apply nowadays, but the concept of a broken shidduch is serious. Below we find the nusach of a Shtar Mechila as formulated by Rav Moshe Shternbuch Shlita of the EIda HaChareidis in Yerushalayim. It should be signed as soon as possible. There is, of course, no deadline as to when the form is signed, and it is often done many years later. However, it is good and proper to do it as soon as possible.
אני החתום מטה החתן __________ בן ____________ מוחל לכלה ________ בת _________ על עלבוני בלב שלם ומסכים לפוטרה מכל חיוב ושעבוד שבעולם. ובאתי עה”ח יום _______________
________ בן _______
אני החתומה מטה הכלה __________ בת ____________ מוחלת לחתן ________ בן _________ על עלבוני בלב שלם ומסכימה לפוטרו מכל חיוב ושעבוד שבעולם. ובאתי עה”ח יום _______________
________ בת _______