Many people wrongly believe that if an agreement is not put in writing they are not required to honour the agreement. This is incorrect (except for some exceptions, one of which is noted below). A verbal agreement may be enforced by either party to the agreement regardless of whether that agreement is in writing. So be careful what you agree!
The difficulty you may have guessed is, proving what was agreed. Indeed we see many agreements, even written agreements that are very unclear. There is sometimes so little detail or, so little care taken, that it is difficult to know what the parties are intending.
In the event that you are making an agreement the words you choose must be written so that, they can be interpreted only one way. This is what often makes legal language appear so cumbersome and difficult to read.
So what contracts are required to be in writing? In short contracts relating to land must be evidenced in writing. This does not necessarily mean that the contract needs to be written but there must be sufficient evidence of it in writing.
The reason for this in Queensland is section 159 of the Property Law Act. This section provides:
No action may be brought upon any contract for the sale or other disposition of land or any interest in land unless the contract upon which such action is brought, or some memorandum or note of the contract, is in writing, and signed by the party to be charged, or by some person by the party lawfully authorised.
In other words, a court is not entitled to enforce a contract that is not evidenced in writing even if the contract is proven to exist. There are also some exceptions to section 59 however these exceptions are complicated and will not be referred to at this time.