Compromising a Doubtful Loan and Ribbis

First let's get the case:

Reuven lends \$100 to Shimon to be paid back in a year. There is no record of the amount of the loan.

And then, one month later, one of the following happen:

• Shimon approaches Reuven, and offers him the \$100 he owes. Reuven, however, refuses and claims that the original amount was actually \$50.
• Shimon approaches Reuven, and offers him the \$50 he thinks he owes. Reuven, however, refuses and claims that the original amount was actually \$100.
• Shimon approaches Reuven, and offers tells him, "I know I owe you money, but I don't remember if it was \$50 or \$100." Reuven agrees that he also cannot recall, but he does remember it was either \$50 or \$100.

Reuven and Shimon are good friends, and honest people. They also realize that they both are not really sure of how much was owed, and recognize that they each may be mistaken. So Reuven and Shimon both agree that Shimon should pay back \$75 as a compromise.

So, is this allowed, or is it a case of ribbis? And if it's allowed, why is it not ribbis?

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I recall from learning Hilchos Ribbis that one may pay back a loan until he is sure that he owes no more money, even if he will possibly be repaying more than he actually borrowed. I'll try to find the source. – jake Jun 20 '11 at 23:02

This is precisely what the beis din would try to do lechatechilah- the Halachic term is p'sharah. It is the best outcome as it creates peace. (Shulchan Aruch C.M. 12:2; S'ma 6)

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"or is it a case of ribbis" : I suppose I should've been more specific: Why is this not ribbis? – yydl Jun 21 '11 at 0:26
@yydl, the reason this would not be ribbis is because the potentially extra \$25 is not payment for the use of the money over the duration of the loan; rather it is to ensure that the lender is payed back sufficiently for that which he actually lent you. (כללא דרביתא כל אגר נטר ליה.) – jake Jun 21 '11 at 0:48