Whether the minor sign fitness is valid can be divided into the following situations:
 1. In principle, a contract concluded by a minor under the age of 8 is invalid. However, it is valid after being ratified by the legal representative.
 2. Minors aged 8-16 years old are valid when they sign contracts for pure benefits. Other contracts are only valid after being ratified by the legal representative.
 3. A contract is signed by a minor who has reached the age of 16 but not the age of 18 and whose main source of income is their own labor income. As long as the contract has no other validity flaws, the contract is valid.
 [Legal Basis]
 Article 18 of the Civil Code states that adults are persons with full capacity for civil conduct and can independently perform civil legal acts.
 Minors over the age of 16 who take their own labor income as their main source of income shall be regarded as persons with full capacity for civil conduct.
 In Article 19 of the Civil Code, minors over the age of eight are persons with limited capacity for civil conduct, and when performing civil legal acts, they shall be represented by their legal representatives or approved and ratified by their legal representatives;
 However, they may independently perform civil legal acts that are purely beneficial or that are appropriate to their age and intelligence.
 Article 20 of the Civil Code states that minors under the age of eight are persons without capacity for civil conduct, and their legal representatives shall act as agents for civil legal acts.