How to make so that the form can be used once?

There is a model:

class Model(models.Model):
 . . .
 is_checked = models.BooleanField(default=False)

And in the view:

form = Form(request.POST or None)

 if request.method == 'POST':
 if form.is_valid:
 . . .
 form.save()

How to make so that the form can only be used once?