Sometimes you want to find out if instances are not tagged with some Tag key, for example if you are grouping your instances with tag "Project" or similar.

You can use the following script for that which will send SNS notification and also e-mail with all instances which doesn't have particular tag, showing you how many instances are running in total.

Change SNS topic to your one and also e-mail source and recipients.

Script can be downloaded from official Cloudhowto GitHub repository.