Enabling or disabling input fields
From your code it looks like you're changing one of "enabled" options only in one of the five cases. You can do that with a loop, using a class selector.

Also, it may be just me, but I don't think you should use value in an input box / radio button to store something different than the default value that you want that item to have. I suggest changing it to something like value_type. 

So, what you can do is add another class to your input elements, select by that and do what you need, something like:

$(function() {
    $('input.entity-option').change(function() {
    if (this.value_type === "I") {
        $("#user_ssn").prop("disabled", false);
        $("#user_ein").prop("disabled", true);
      } else {
        $("#user_ssn").prop("disabled", true);
        $("#user_ein").prop("disabled", false);
      }
    });
  });


And in your HTML you need something like:

&lt;span class="radio inline"&gt;
  &lt;label for="user_entity_type_i"&gt;
    &lt;input class="radio_buttons required entity-option" required="required" aria-required="true" type="radio" value_type="I" name="user[entity_type]" id="user_entity_type_i" /&gt;
    Individual / Sole Proprietor
  &lt;/label&gt;
&lt;/span&gt;

&lt;span class="radio inline"&gt;
  &lt;label for="user_entity_type_c"&gt;
    &lt;input class="radio_buttons required entity-option" required="required" aria-required="true" type="radio" value_type="C" name="user[entity_type]" id="user_entity_type_c" /&gt;
    Corporation
  &lt;/label&gt;
&lt;/span&gt;

&lt;span class="radio inline"&gt;
  &lt;label for="user_entity_type_p"&gt;
    &lt;input class="radio_buttons required entity-option" required="required" aria-required="true" type="radio" value_type="P" name="user[entity_type]" id="user_entity_type_p" /&gt;
      Partnership
  &lt;/label&gt;
&lt;/span&gt;

&lt;span class="radio inline"&gt;
  &lt;label for="user_entity_type_l"&gt;
    &lt;input class="radio_buttons required entity-option" required="required" aria-required="true" type="radio" value_type="L" name="user[entity_type]" id="user_entity_type_l" /&gt;
    Limited Liability Company
  &lt;/label&gt;
 &lt;/span&gt;

 &lt;span class="radio inline"&gt;
   &lt;label for="user_entity_type_o"&gt;
     &lt;input class="radio_buttons required entity-option" required="required" aria-required="true" type="radio" value_type="O" name="user[entity_type]" id="user_entity_type_o" /&gt;
       Other
   &lt;/label&gt;
 &lt;/span&gt;