from django.contrib.auth.models import User
from Scanner.models import T
class SubmitD(ModelForm):
    #model form fields here

    class Meta:
        model = T
        fields = ['field1','field2']

    def save(self, request):
        instance = self.cleaned_data
        #other fields
        current_user = request.user
        d.FKtoClient_id = current_user.id
        d.save()

current_user = request.user
d.FKtoClient_id = current_user.id

(1048, "Column 'FKtoUser_id' cannot be null")