To be a valid will, the document must be testamentary in nature, a free expression of the testator’s wishes with respect to the distribution of his or her estate upon death, and conform to the requirements of execution set out in Part I of the Succession Law Reform Act. 

The common challenges to the validity of a will are:

• Non-compliance with the requirements of due execution;
• Lack of testamentary capacity;
• Lack of knowledge and approval of the contents of the will (taking into consideration any “suspicious circumstances”); and
• Presence of undue influence.