title: Update Managed Metadata value using REST in Sharepoint 2013
body: <p>I'm able to <strong>update a 'normal' Metadata value</strong> via my REST call.
  I'm also trying to <strong>update a Managed Metadata value</strong> via the same call. </p>
  
  <p>I'm getting <strong>no errors.</strong> 
  The normal value <strong>gets updated as as expected</strong>, but the MMD value <strong>stays emtpy</strong>.</p>
  
  <p><strong>Here's my sample Code:</strong></p>
  
  <pre><code>//DEMO URL
  var url = "[...]/_api/Web/Lists(guid'nnnnnnnn-nnnn-nnnn-nnnn-nnnnnnnnnnnn')/Items(nn)";
  
  var updateObject = {};
  
  //MANAGED METADATA FIELD FOR SETTING
  updateObject["MMD_FIELD"] = {
      "__metadata": { "type": "SP.Taxonomy.TaxonomyFieldValue" },
      "Label": "nn",
      "TermGuid": "047cb946-451d-45bf-882a-52e47e97a871",
      "WssId": -1
  };
  
  //NORMAL METADATA "TEXT-FIELD" FOR SETTING
  updateObject["Subject"] = "WORKS";
  
  //FILETYPE
  updateObject["__metadata"] = {'type':'SP.ListItem'};
  
  //AJAX CALL     
  $.ajax({
  
      url: url,
      type: "POST",
      data: JSON.stringify( updateObject ),
      headers: { 
        "Accept": "application/json;odata=verbose ",
        "Content-Type": "application/json;odata=verbose ",
        "X-RequestDigest" : $("#__REQUESTDIGEST").val(),
        "X-HTTP-Method": "MERGE",
        "If-Match": "*"
     }
  
  });
  </code></pre>
  
  <p>After that the 'Subject' of the File is 'WORKS' - <strong>but there's no chance to update a Managed Metadata Field.</strong></p>
  
  <p><strong>Tried:</strong></p>
  
  <ul>
  <li>Some other MMD-Fields</li>
  <li>Defined ETag in "If-Match"</li>
  <li>Some other X-HTTP-Methods ( PATCH ... )</li>
  <li>Other Terms etc.</li>
  <li>GUID, Label and Name are 100% right</li>
  <li>Tried normal and mmd value in seperate calls</li>
  </ul>