Consensus

Article 93
The parties may dissolve the contract upon consensus through consultation. The parties may stipulate the conditions for dissolusion of the contract by either party. When the conditions for dissolusion of the contract mature, the party with the right to dissolve may dissolve the contract.
Article 105
If the creditor exempts the debtor from its liabilities in whole or in part, the rights and obligations under the contract shall terminate in whole or in part.
Article 2.106 (ex art. 5.106 B) - Written Modification only 84
(1) A clause in a written contract requiring any modification or ending by agreement to be made in writing establishes only a presumption that an agreement to modify or end the contract is not intended to be legally binding unless it is in writing. 85
(2) A party may by its statements or conduct be precluded from asserting such a clause to the extent that the other party has reasonably relied on them. 86
§ 213 Effect of Integrated Agreement on Prior Agreements (Parol Evidence Rule)
§ 213 Effect of Integrated Agreement on Prior Agreements (Parol Evidence Rule)
(1) A binding integrated agreement discharges prior agreements to the extent that it is inconsistent with them.
(2) A binding completely integrated agreement discharges prior agreements to the extent that they are within its scope.
(3) An integrated agreement that is not binding or that is voidable and avoided does not discharge a prior agreement. But an integrated agreement, even though not binding, may be effective to render inoperative a term which would have been part of the agreement if it had not been integrated. 
CHAPTER 12 - DISCHARGE BY ASSENT OR ALTERATION
Topic 1 - The Requirement of Consideration
§ 273 Requirement of Consideration or a Substitute
Except as stated in §§ 274-77, an obligee's manifestation of assent to a discharge is not effective unless
(a) it is made for consideration, 
(b) it is made in circumstances in which a promise would be enforceable without consideration, or
(c) it has induced such action or forbearance as would make a promise enforceable.
§ 274 Cancellation, Destruction or Surrender of a Writing
An obligee's cancellation, destruction or surrender to the obligor of a writing of a type customarily accepted as a symbol or as evidence of his right discharges without consideration the obligor's duty if it is done with the manifested intention to discharge it.
§ 275 Assent to Discharge Duty of Return Performance
If a party, before he has fully performed his duty under a contract, manifests to the other party his assent to discharge the other party's duty to render part or all of the agreed exchange, the duty is to that extent discharged without consideration.
§ 276 Assent to Discharge Duty to Transfer Property
A duty of an obligor in possession of identified personal property to transfer an interest in that property is discharged without consideration if the obligee manifests to the obligor his assent to the discharge of that duty.
§ 277 Renunciation 
(1) A written renunciation signed and delivered by the obligee discharges without consideration a duty arising out of a breach of contract.
(2) A renunciation by the obligee on his acceptance from the obligor of some performance under a contract discharges without consideration a duty to pay damages for a breach that gives rise only to a claim for damages for partial breach of contract
Topic 2 - Substituted Performance, Substituted Contract, Accord and Account Stated
§ 278 Substituted Performance
(1) If an obligee accepts in satisfaction of the obligor's duty a performance offered by the obligor that differs from what is due, the duty is discharged.
(2) If an obligee accepts in satisfaction of the obligor's duty a performance offered by a third person, the duty is discharged, but an obligor who has not previously assented to the performance for his benefit may in a reasonable time after learning of it render the discharge inoperative from the beginning by disclaimer.
§ 279 Substituted Contract
(1) A substituted contract is a contract that is itself accepted by the obligee in satisfaction of the obligor's existing duty.
(2) The substituted contract discharges the original duty and breach of the substituted contract by the obligor does not give the obligee a right to enforce the original duty.
§ 280 Novation
A novation is a substituted contract that includes as a party one who was neither the obligor nor the obligee of the original duty.
§ 281 Accord and Satisfaction
(1) An accord is a contract under which an obligee promises to accept a stated performance in satisfaction of the obligor's existing duty. Performance of the accord discharges the original duty.
(2) Until performance of the accord, the original duty is suspended unless there is such a breach of the accord by the obligor as discharges the new duty of the obligee to accept the performance in satisfaction. If there is such a breach, the obligee may enforce either the original duty or any duty under the accord.
(3) Breach of the accord by the obligee does not discharge the original duty, but the obligor may maintain a suit for specific performance of the accord, in addition to any claim for damages for partial breach.
§ 282 Account Stated
(1) An account stated is a manifestation of assent by debtor and creditor to a stated sum as an accurate computation of an amount due the creditor. A party's retention without objection for an unreasonably long time of a statement of account rendered by the other party is a manifestation of assent.
(2) The account stated does not itself discharge any duty but is an admission by each party of the facts asserted and a promise by the debtor to pay according to its terms.
Topic 3 - Agreement of Rescission, Release and Contract Not to Sue
§ 283 Agreement of Rescission
(1) An agreement of rescission is an agreement under which each party agrees to discharge all of the other party's remaining duties of performance under an existing contract.
(2) An agreement of rescission discharges all remaining duties of performance of both parties. It is a question of interpretation whether the parties also agree to make restitution with respect to performance that has been rendered
§ 284 Release
(1) A release is a writing providing that a duty owed to the maker of the release is discharged immediately or on the occurrence of a condition.
(2) The release takes effect on delivery as stated in §§ 101-03 and, subject to the occurrence of any condition, discharges the duty.
§ 285 Contract Not to Sue
(1) A contract not to sue is a contract under which the obligee of a duty promises never to sue the obligor or a third person to enforce the duty or not to do so for a limited time.
(2) Except as stated in Subsection (3), a contract never to sue discharges the duty and a contract not to sue for a limited time bars an action to enforce the duty during that time.
(3) A contract not to sue one co-obligor bars levy of execution on the property of the promisee during the agreed time but does not bar an action or the recovery of judgment against any co-obligor.
Article 407. The Grounds for the Termination of Obligations
1. The obligation shall be terminated in full or in part on the grounds, stipulated by the present Code, by the other laws and the other legal acts, or by the contract.
2. The termination of the obligation upon the claim of one of the parties shall be admitted only in the cases, stipulated by the law or by the contract.
Article 409. The Indemnity
By an agreement between the parties, the obligation may be terminated by way of paying an indemnity instead of the discharge (the payment of money, the transfer of the property, etc.). The amount, the term and the procedure for paying the indemnity shall be established by the parties.
Article 414. Termination of the Obligation by the Novation
1. The obligation shall be terminated by an agreement between the parties on replacing the primary obligation, which has existed between them, with another obligation between the same persons, stipulating a different object or a different way of the discharge (the novation).
2. The novation shall not be admissible with respect to the obligations on the compensation for the harm, inflicted to the life or to the health, and also with respect to those on the alimony.
3. The novation shall terminate the additional liabilities, connected with the primary obligation, unless otherwise stipulated by the agreement between the parties.
Article 415. Forgiving the Debt
The obligation shall be terminated by the creditor's absolving the debtor from the obligations, borne by him, if this does not violate the rights of the other persons with respect to the creditor's property.
Article 450. The Grounds for the Amendment and the Cancellation of the Contract
1. The amendment and the cancellation of the contract shall be possible only by an agreement between the parties, unless otherwise stipulated by the present Code, by the other legal acts or by the contract.
2. Upon the demand of one of the parties, the contract may be amended or cancelled by the court decision only:
1) in case of an essential violation of the contract by the other party;
2) in the other cases, stipulated by the present Code, by the other legal acts or by the contract. As an essential violation shall be recognized such violation of the contract by one of the parties, which entails for the other party the losses, to a considerable extent depriving it of what it could have counted upon when concluding the contract.
3. In case of the unilateral refusal to discharge the contract in full or in part, when such refusal is admitted by the law or by the agreement between the parties, the contract shall be correspondingly regarded as cancelled or as amended.