(based around Shoel U’meishiv I:II:186)
[The ruling in a din Torah awarded Reuven the profits due to him as a partner in Shimon’s business after Reuven would accept a cherem (serious ban/curse) if he was lying. Beit din referred to "the calculated amount" but did not state what it was. Reuven tried to collect the payment from Shimon with the help of an officer of the court, but Shimon refused to pay. Some time later, Shimon died, and Reuven has presented the beit din ruling to the same beit din to collect from the inheritors. Beit din does not know if Shimon had paid the award at some time in his lifetime and also does not remember how much money the partnership was worth at the time of the award (it was regrettably not written in the ruling).]
Beit din decided that since the ruling is in Reuven’s possession, it is as if Reuven has a loan document, in which case Shimon’s inheritors cannot claim that their father paid the amount due (see Shach 39:31). The S’ma (70:19) distinguishes between a document of beit din, regarding which he is not believed without proof that he paid, and a simple ruling, regarding which he can make that claim because it is made to be paid immediately. However, this ruling is like a beit din document because it states that Reuven will first have to accept a cherem, which he did not yet do. This is along the lines of the rule that whoever needs to swear in order to win the case, is not considered to have won until the oath is taken. Also, since Shimon was asked by beit din to pay, and he did not do so when asked, he is considered like one who does not listen to beit din. In such a case, it is not relevant whether the ruling is considered like a document of beit din or not, and he is not believed without proof that he paid.
The question, though, is whether it is only the person who was obligated who is not believed he paid without proof or even his inheritors, from whom it is often more halachically difficult to extract payment. Even if we wanted to claim that the occurrence that the father paid in these circumstances before his death is uncommon, inheritors might still be able to make the claim. After all, we see that we make even the uncommon claim that an oness (extenuating circumstance) happened to an object being watched before extracting payment from inheritors. Payment is also not so unexpected since accepting a cherem happens more easily than taking an oath. The fact that the father originally refused to pay is also not that pertinent since it is very possible that before his death he decided it was time to pay.
Additionally, since the ruling does not state how much Shimon owed Reuven, it is possible to make the claim on behalf of the inheritors that the amount owed was the smallest amount imaginable and not what Reuven claims it was. This is similar to the circumstance of a document of debt that refers to a denomination in the plural but is missing the number, in which case he pays only two units of the denomination (see Shulchan Aruch, Choshen Mishpat 88). On the other hand, since Reuven would not be believed to extract money without going back to beit din to determine how much he deserves and this did not happen, Reuven is at least believed regarding this smaller amount.
305 - Backing Out of the Sale of Wine Due to Non-Payment
306 - Payment of Din Torah Award by a Litigant’s Orphans
307 - When the Defendant Goes to the Plaintiff’s Place