In 2018, K-IFRS No. 1109 (Financial Instrument) was Introduced. It was that firms were forced to allocate additional their allowance for bad debts. So This study analyze the change of allowance for bad debts after the government introduced K-IFRS No. 1109 (Financial Instrument). We also investigated whether this change can have an effect on firm"s conservative. In addition, we analyze value of allocate allowance for bad debts. Results of analyze are below. First, We was expected majority of firms to set up their allowance for bad debts higher. but, Some of firms allocated more allowance for bad debts. That firms also showed higher conservative compared to the other firms. Secondly, it was negative relationship between additional allowance for bad debts and firm"s value. So, we find out that CEO tries to recognize their loss timely and decrease uncertain about future loss, get their interested parties understand possibility of firm"s future revenue and growing. That"s why firms set-up more allowance for bad debts. Finally, In higher conservative firms, the allocation to additional allowance for bad debts tended to prevent firm"s value from going down relatively.