Here are the steps to follow:
1. Navigate to Lists > Search > Saved Searches > New > Transaction
2. Under the Criteria tab > Standard sub tab > add the following filters:
Type = Invoice
Days Overdue = is greater than or equal to 30
*Add additional filters like sales rep or Name as needed
3. Under the Results tab > Columns sub tab > add the fields that user wishes for the recipients to see
4. Under the Email tab > set Send Email According to Schedule = True
5. Set recipients under the Specific Recipients tab or the Recipients from Results sub tab
6. Under the Schedule sub tab > set the radio button to the frequency on which recipients will be receiving the email.
*Set to Daily Event if user needs to send alert to customers as soon as invoice reaches 30 days overdue.