There are a few different acts that regulate how wills must be prepared in order for them to be valid. There are specific requirements setting out how a will must be signed and witnessed. There are also specific requirements that must be met in order to make changes to an existing will. If your will is found to be invalid after you die because one of the legal requirements for preparing a will was not met, then the courts will deem that you died without a will. If this is the case, then your estate will be distributed in accordance with the Estate Administration Act and none of the provisions in your will can be considered. Getting professional help from a lawyer to prepare your will minimizes the chances of your will being found to be invalid.