You need to add the annotation `[HttpPost]` to your Action and change the return type to `JsonResult`..

    public class WorkingController : Controller
    {
        // GET: Working
        public ActionResult Index()
        {
            return View();
        }

        [HttpPost]
        public JsonResult Save(WorkingModel model)
        {
            // All model properties are null here????

            return Json("Success");
        }
    }

For more info have a look here: http://www.dontpaniclabs.com/blog/post/2013/02/27/posting-json-data-to-an-mvc-controller-via-ajax/

EDIT:

If you still are getting nulls inside of Save, change to:

    public class WorkingController : Controller
        {
            // GET: Working
            public ActionResult Index()
            {
                return View();
            }

            [HttpPost]
            public JsonResult Save([FromBody]WorkingModel model)
            {
                // All model properties are null here????

                return Json("Success");
            }
        }

Sorry I can't fully remember when you have to use From Body and when you don't have to use, so try the first code first then try this

EDIT:

Also look into what `JSON.stringify` is producing... maybe its failing and sending null up.

EDIT 2: