diff --git a/apps/inm/serializers.py b/apps/inm/serializers.py
index 192c8ce4..881315b8 100644
--- a/apps/inm/serializers.py
+++ b/apps/inm/serializers.py
@@ -231,7 +231,8 @@ class MIODoSerializer(CustomModelSerializer):
         fields = ['id', 'number', 'note', 'do_user',
                   'belong_dept', 'type', 'inout_date', 'mgroup', 'mio_user']
         extra_kwargs = {'inout_date': {'required': True}, 
-                        'do_user': {'required': True}, 'number': {"readonly": True}}
+                        'do_user': {'required': True}}
+        read_only_fields = ["number"]
 
     def validate(self, attrs):
         if 'mgroup' in attrs and attrs['mgroup']:
@@ -285,7 +286,8 @@ class MIOPurSerializer(CustomModelSerializer):
     class Meta:
         model = MIO
         fields = ['id', 'number', 'note', 'pu_order', 'inout_date', 'supplier', 'mio_user']
-        extra_kwargs = {'inout_date': {'required': True}, 'number': {"readonly": True}}
+        extra_kwargs = {'inout_date': {'required': True}}
+        read_only_fields = ["number"]
 
     def create(self, validated_data):
         validated_data['type'] = MIO.MIO_TYPE_PUR_IN
@@ -312,7 +314,8 @@ class MIOOtherSerializer(CustomModelSerializer):
         model = MIO
         fields = ['id', 'number', 'note', 'supplier',
                   'customer', 'type', 'inout_date', 'mio_user']
-        extra_kwargs = {'inout_date': {'required': True}, 'number': {"readonly": True}}
+        extra_kwargs = {'inout_date': {'required': True}}
+        read_only_fields = ["number"]
 
     def create(self, validated_data):
         validated_data['number'] = MIO.get_a_number(validated_data["type"])