Updating a list item in SharePoint using the REST service is pretty straight forward once you know what to put and what data to call.

In this example we’ll be looking at making the call from MS Flow, however the same applies to any other service you wish to use including SharePoint 2013 workflows.

Some caveats to be aware of:

  1. When making an update query the POST method must be used combined with the X-HTTP-method of MERGE to let the system know what type of operation you are committing.
  2. You must include a normal field like the “Title” field as the first field in the query to update, it won’t actually update the field if you use the same value as the original one – this one is important as you will get the error message