Most contracts can be either written or oral, but some agreements must be in writing in order to be binding in the court of law. The following agreements must be executed in writing, in a legal contract:
real estate sales and purchases
agreements to pay someone else's debts (eg. Promissory Notes)
contracts that take longer than one year to complete
real estate leases for longer than one year (eg. Rental/ Lease Agreement)
contracts for over a certain amount of money (depending on the state)
contracts that will last longer than the life of the party performing the contract (eg. Power of Attorney)
a transfer of property at the death of the party performing the contract
Although other types of contracts may be oral, it is advisable to "get it in writing" to insure both parties understand their obligations. If court enforcement is required, a written contract shows the parties' obligations and avoids a "he said, she said" dispute.