Demand is necessary to make an obligation due.

The rule that in case of extraordinary inflation or deflation of the currency stipulated should supervene, the value of the currency at the time of the establishment of the obligation shall be the basis of payment of obligations arising from law.

"A proof that an act could have been done is no proof that it was actually done” supports the concept known as tender of payment.

An agreement to pay a promissory note in dollars, while null and void under RA 529 does not defeat a creditor’s claim.

Obligations requiring payment in foreign currency must be discharged in Philippine currency as provided by RA 8183.

When the obligee accepts the performance knowing its incompleteness or irregularity, the obligation is deemed fully complied with.

Where an application for a loan of money was approved, there arises a perfected contract before the delivery of the object of the contract.

It is a concept that derives from the principle that since mutual agreement can create a contract, mutual disagreement can cause its extinguishment.

No person shall be responsible for those events which could not be foreseen, or which though foreseen, were inevitable.