legal ground
Article 490 of the Civil Code
If the parties enter into a contract in the form of a contract, the contract shall be established when the parties sign, seal or press their fingerprints. Before signing, sealing or fingerprinting, one party has fulfilled its main obligations, and the contract is established when the other party accepts it.
Article 557
Creditor's rights and debts shall be terminated under any of the following circumstances:
(a) The debt has been fulfilled.
(2) The debts offset each other;
(3) The debtor deposits the subject matter according to law.
(4) Creditors are exempted from debts;
(5) Creditor's rights and debts are owned by one person;
(six) other circumstances stipulated by law or agreed by the parties to terminate.
If the contract is terminated, the rights and obligations of the contract shall be terminated accordingly.
Article 558
After the termination of creditor's rights and debts, the parties concerned shall abide by the principle of good faith and fulfill their obligations such as notification, assistance, confidentiality and recycling of old things in accordance with trading habits.