In financial obligations, deficient performance arises when the original object is returned but its legal position is still impaired by another liability or claim. A usurped item, for example, may have become encumbered by a debt or a liability generated during the usurpation.
The question is whether the owner merely received the physical item or received it free of the legally relevant impairment. If some of the owner's rights remain unsatisfied, full discharge cannot simply be inferred from the physical handover.
Principle: A change in possession does not invariably establish complete legal performance; associated rights must also be considered.