Settlement: Annulling a Settlement
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 2179
If two people conclude a settlement with each other with respect to something, they can annul the settlement with each other’s consent. Also, if in the transaction (muʿāmalah) they stipulate a right for both or one of them to annul the transaction, the person who has that right can annul the settlement.
-Ayatullah Sistani, Practical Laws of Islam, Settlement (Sulh)