Contracts are most commonly discharged by way of performance, by the parties, of their contractual obligations.
As a general rule, for a contract to be discharged by performance the contractual obligations must be performed completely and exactly; it is not sufficient to 'substantially' perform a contract.
Exceptions to the general rule
There are, however, some exceptions to the rule that exact performance is required. The parties may also modify this requirement - by expressly or implicitly providing that exact performance is not required. Determining the relevant level of performance will, therefore, depend on proper construction of the contract involved.
Detailed discussion forthcoming