Group 1 - The concept of "contribution salary" refers to the salary included in the total salary statistics as per national statistical department regulations, which should be declared based on the previous year's average monthly salary [3] - The contribution base is determined by the contribution salary, with specific rules for minimum and maximum limits based on provincial average salaries [3] - For new employees, the contribution salary is based on their starting salary for the first month, and thereafter it is determined by the previous year's average salary [3] Group 2 - If an employer discovers an error in the declared contribution salary before completing the social insurance fee declaration, they can modify the contribution salary through the original submission method [4] - If the social insurance fee declaration has been completed but not paid, adjustments can be made by voiding the declaration and modifying the contribution salary [4] - For adjustments to the contribution salary after the declaration has been completed and paid, employers must provide relevant documentation to the tax authority to process the change [4] Group 3 - When an employee resigns and later returns to the company, they are considered a new insured person, and the employer must declare a new contribution salary for them [4]