$mysql_hostname = "localhost";
$mysql_user = "root";
$mysql_password = "";
$mysql_database = "loan";
$connect = mysql_connect($mysql_hostname, $mysql_user, $mysql_password) 
or die("Something went wrong...");
mysql_select_db($mysql_database, $connect) or die("Something went wrong...");

    $datess = $_POST['datess'];
    $control = $_POST['control'];  
    $payee = $_POST['payee'];                            
      if(!empty($datess) && !empty($control) && !empty($payee))
                  mysql_query("INSERT INTO `sales`(`datess`, `control`, `payee`)
                   VALUES ('$datess', '$control', '$payee')");
            //   echo "<script type='text/javascript'>alert('Please Dont Leave Blank Field.')</script>";


    ?> <html> <body> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> <link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css"> <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script> <script src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script> </head> <center> <form action="" method="post"> <label>
      <input type="text" name="datess"> </label> <label>
      Control Number
      <input type="number" name="control"> </label> <label>
      <input type="text" name="payee"> </label> </form> <!-- Trigger the modal with a button --> <div class="usman"> <button type="submit" name="btn_submit" class="btn btn-info" data-toggle="modal" data-target="#myModal" tabindex="14"><strong>Confirm</strong></button> </div> <!-- Modal --> <div class="modal fade" id="myModal" role="dialog"> <div class="modal-dialog"> <!-- Modal content--> <div class="modal-content"> <div class="modal-header"> <h5 class="modal-title">Confirmation</h5> </div> <div class="modal-body"> <h4><font color="red"> Are you sure ? </font></h4> </div> <div class="modal-footer"> <button type="BtnClose" class="btn btn-warning" data-dismiss="modal">Close</button> <button type="submit" name="submit" class="btn btn-success"  data-dismiss="modal">Save</button> 

What error do you get?

maybe remove the qoutes from your variables, so they are not treated as strings?

mysql_query('INSERT INTO sales 
                (datess, control, payee)
                 ('.$datess.', '.$control.', '.$payee.')');

Note that you should be using mysqli, with i at the end. Mysql is deprecreated in the latest PHP versions I think. Or use PDO for a full object oriented approach.