A signed and undated will is invalid. According to the relevant laws and regulations, a self-written will should be written and signed by the testator, indicating the year, month and day. And the will must express the true meaning of the testator, and the will made by fraud or coercion is invalid.

Legal objectivity:

Article 143 of the Civil Law of People's Republic of China (PRC) is valid if a civil juristic act meets the following conditions: (1) The actor has corresponding capacity for civil conduct; (2) the meaning is true; (three) does not violate the mandatory provisions of laws and administrative regulations, and does not violate public order and good customs. Article 143 of the General Principles of the Civil Law of People's Republic of China (PRC) * * * The will made by a person without or with limited capacity for civil conduct is invalid. A will must express the true meaning of the testator, and a will made by fraud or coercion is invalid. Forged wills are invalid. If the will is tampered with, the tampered contents are invalid. Article 134 of the Civil Code of People's Republic of China (PRC) * * * A self-written will is written and signed by the testator, indicating the year, month and day.