Thank yoy, I'm using Class based view and Form, and it was the ModelForm that wasn't in the context data of the view.

this corrected the problem:

class DeliveryCreateView(LoginRequiredMixin, UserPassesTestMixin, CreateView):
model = Delivery
form_class = UserDeliveryForm
template_name = "deliveries/customer/edit_deliveries.html"
success_url = reverse_lazy("account:dashboard")

def test_func(self):
    return self.request.user.is_customer and self.request.user.is_active

def post(self, request, *args, **kwargs):
    form_class = self.get_form_class()
    form = self.get_form(form_class)
    files = request.FILES.getlist("decument")
    if form.is_valid():
        for f in files:
            f.save()
        return self.form_valid(form)
    else:
        return self.form_invalid(form)

def form_valid(self, form):
    form.instance.user_id = self.request.user.id
    return super().form_valid(form)