The handwritten commitment letter is valid. The effectiveness of the letter of commitment depends on: the will of the parties is true and does not violate the principle of voluntariness; The actor has corresponding capacity for civil conduct; Do not harm the interests of the state, the collective or the third party; Do not violate the law, do not violate public order and good customs.

legal ground

Article 5 of the Civil Code of People's Republic of China (PRC)

Civil subjects engaged in civil activities should follow the principle of voluntariness and establish, change and terminate civil legal relations according to their own wishes.

Article 7

Civil subjects engaged in civil activities should follow the principle of good faith and adhere to honesty and trustworthiness.

Article 8

Civil subjects engaged in civil activities shall not violate the law or public order and good customs.

Article 143

A civil juristic act that meets the following conditions is valid:

(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.