일부ㆍ불완전 이행과 동시이행항변권의 인정 범위

Our majority theory and precedent states that in the case of selling real estate for which a mortgage registration has been completed, unless there are special circumstances such as the buyer assuming the secured debt of the mortgage and deducting the amount of said debt from the purchase price, the seller's obligation to register the transfer of ownership, the obligation to deliver, and the obligation to cancel the mortgage registration are concurrently performed with the buyer's obligation to pay the balance of the purchase price. If the seller performs all of the above obligations, the buyer cannot exercise the defence right of simultaneous performance against the seller's claims regarding the buyer's obligations. However, if the seller performs only the obligation to register the transfer of ownership and the obligation to deliver, and does not perform the obligation to cancel the mortgage registration, the scope of the balance for which the buyer can refuse performance based on the defence right of simultaneous performance is the entire amount or is limited to part of it(the maximum amount of the mortgage claim). The scope of the defence right of simultaneous performance is a matter related not only to the establishment conditions and effect of the above right, but also to its legislative intent(legislative history and function, etc.). Accordingly, I have drawn a conclusion through comparative legal review of the civil law provisions of Germany and Japan that have influenced our legislation. First, a debtor who has received partial or incomplete performance from the other party may, in principle, exercise the defence right of simultaneous performance for all of his obligation, regardless of whether his obligation are divisible or indivisible. However, when the debtor's obligation is divisible, if the unperformed portion of the other party's obligation is small or insignificant and it is unclear whether the debtor has the will or ability to perform the obligation, and it is judged that refusal to perform the entire obligation would be against fairness and good faith, the right to object may be exercised only for the portion of the obligation equivalent to the unperformed portion of the other party's obligation. Accordingly, even if the buyer of real estate for which a mortgage registration has been completed has received performance of the obligation to transfer ownership and the obligation to deliver from the seller, in principle, he or she can exercise the defence right of simultaneous performance for the entire balance until the obligation to cancel the mortgage registration is performed or offered for performance.