1. Low accident rate at work: Work-related injury insurance is the insurance purchased by the employer for employees, which is mainly used to guarantee medical care and living allowance for employees in case of accidental injuries or occupational diseases at work. If the accident rate of this unit is low, then the work-related injury insurance premium paid by the unit is relatively low, resulting in insurance balance.

2. Limitation of reimbursement standard: The reimbursement standard of industrial injury insurance is stipulated by the state, and there may be some restrictions, such as certain treatment items or drugs are not included in the reimbursement scope, or the reimbursement ratio is low. If the medical expenses of injured workers are lower than the reimbursement standard, there will be a balance of insurance expenses.

3. Changes in the number of participants: The number of employees in the company may change. If the work-related injury insurance premium paid by the company is calculated according to the number of old employees, but the number of new employees is small, then the insurance premium has a balance.

4. Fund accumulation: The insurance expenses of industrial injury insurance usually accumulate in the fund. If the previous work-related injury insurance expenses exceed the previous work-related injury insurance expenses, then the fund has a balance.