Specifying text format when creating field on custom node type
Set the 'format' =&gt; 'filtered_html' to allow filtered html

&lt;?php
    // ...more fields above
        'release_notes' =&gt; array(
          'field_name' =&gt; 'release_notes',
          'type' =&gt; 'text_long',
          'label'  =&gt; $t('Notes'),
          'description'  =&gt; $t('Release notes (e.g. liner notes)'),
          'widget' =&gt; array('type' =&gt; 'text_textarea'),
          'settings' =&gt; array('text_processing ' =&gt; '1'), // Filtered HTML...?
          'format' =&gt; 'filtered_html' // &lt;&lt;--- Set this value to allow filtered HTML
          'weight' =&gt; 9,
        ),
    // ...more fields below
    ?&gt;