If you don't, there are no legal issues. Also, if the annual salary is less than the number of deductible family members (1 person 14.08 million won, 2 people 16.23 million won, 3 people 24.99 million won, 4 people 30.83 million won), the income tax amount is 0, so there is no need to do it. However, it is generally recommended to do year-end tax settlement. Because all of my income could be left unspent. This may result in waiving taxes that may be refunded.