Wills Act 2008

An obliteration, interlineation or other alteration made in any will after the execution of the will is not valid, except so far as the words or effect of the will before the alteration are not apparent, unless the alteration is executed in accordance with Division 2 of this Part or Division 2 of Part 3.

A will, with an alteration as part of the will, is taken to be duly executed if the signature of the testator and the subscription of the witnesses are made in the margin or on some other part of the will opposite or near to the alteration or at the foot or end of, or opposite to, a memorandum referring to the alteration and written at the end or on some other part of the will.