title: Automatically generate a unique sequential ID in Google Sheets
body: <p>In Google Sheets, I have a spreadsheet called Events/Incidents which staff from various branches populate. I want Column B to automatically generate a unique ID based on the year in column A and the previously populated event. Given that there could be several events on a particular day, rows in column A could have duplicate dates. </p>
  
  <p>The following is an example of what I am looking for in column B:</p>
  
  <p><a href="https://i.stack.imgur.com/GzZAC.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/GzZAC.png" alt="ID"></a></p>
  
  <p>There can be no duplicates. Would really appreciate some help with either code or formula.</p>