I've also got another statement directly after the initial statement would this cause a problem?
$add_order_sql = "INSERT INTO ORDERS ( fullname ) values ( '$full_name' )";
mysql_query($add_order_sql, $link) or die("Sorry couldn't add items to table");
$order_id = mysql_insert_id();
print "Thank You. Your Order ID is $order_id. Please quote this in any communication ";
$rm_item_sql = "DELETE FROM TRACKING WHERE user_id = \"$user_id\"";
mysql_query1($rm_item_sql) or die("Couldn't remove items.");