//if (document.getElementsByClassName('chkaddress').checked) {
    $('#DivCommunicationAddress').show();
}
   else {

            $('#DivCommunicationAddress').show();
}

@Html.CustomCheckBoxFor(Employee => Employee.IsActive, new { @class = "ui-checkbox chkaddress" })
    @Html.LabelFor(Employee=>Employee.IsActive, "Same As Home Address")