class Lead(models.Model):
    created_on = models.DateTimeField(auto_now_add=True)
    modified_on = models.DateTimeField(auto_now=True)
    ...
    score = models.DecimalField(decimal_places=3, max_digits=7, blank=True, null=True)
    score_updated_on = models.DateTimeField(blank=True, null=True)
    active = models.BooleanField(default=True)