The transaction has serious consequences for one or both parties

This is an important factor. Even when an agreement is made between family or friends, it may be that the consequences are serious. In such cases the parties will probably want their agreement to be legally enforceable, and have the necessary intention to create a contract. This will be true, for example, if the sum of money involved is large, or if the consequences of not performing the promise are serious.

An example is where persons share in the purchase of a lottery ticket and agree to share the proceeds of any win. The courts have held that such agreements are intended to be legally binding.