MVC C# - The value 'checked' is not valid when I use a checkbox
===

I have a field called W2_Sent which is defined as (bit,null)

In my view I have the following which shows it as a checkbox:

         <div class="editor-label"  style="width: 10em">                        
           @Html.Label("W2 Sent")
         </div>
         <div class="editor-field">
           @Html.EditorFor(model => model.W2_Sent)
           @Html.ValidationMessageFor(model => model.W2_Sent)
         </div>

If I check it, I get an error

The value 'checked' is not valid for W2_Sent

          [HttpPost]
          public ActionResult Create(Employee emp)
          {

            foreach (ModelState modelState in ViewData.ModelState.Values)
            {
                foreach (ModelError error in modelState.Errors)
                {

                    string s = "error";

                }

            }

I am able to trap the error within the foreach loop you see above..

Why am I getting value 'checked' is invalid though
