1. One who barters, agrees with a second party to transfer a certain quantity of his goods or profits to him, or waives his claims or rights against that party in exchange for a certain quantity of the second party’s goods or profits or for the second party waiving his claims or rights against the first party.
2. The two parties must be mature, sane, not under force to barter and not be interdicted by the leading mujahidin from using their wealth.
3. If a debtor owes a creditor a fixed amount of money and the creditor has forgotten the correct amount of the debt and wants to barter the debt at a lower than the correct amount, the debtor must make the creditor aware of his error. If, he does not, the money he withheld is not halal for use.
If the debtor tells the creditor of his error and still convinces him to barter for the reduced price or if the situation is such that even had the creditor been aware of the correct amount he would have still bartered for a lower amount, the money is halal for use.