Ubercart Line item tax not displayed first time
I added the line items at validate. However at that moment the tax is already calculated. What needs to happen is recalc the taxes. This can be done from a ajax call when a field changes value.

function My_Module_update_line_items($form, $form_state) {
  $commands = array();
  if (isset($form['panes']['payment']['line_items'])) {
    $commands[] = ajax_command_replace('#line-items-div', drupal_render($form['panes']['payment']['line_items']));
    $commands[] = ajax_command_prepend('#line-items-div', theme('status_messages'));
  }

  return array('#type' =&gt; 'ajax', '#commands' =&gt; $commands);
}