Planner lets you send your customers their proof of delivery. It will be sent attached by email and therefore, you will have to previously add the emails and activate communication with your clients through Emails.
For this, you must follow these steps:
Messages > Emails
Enable email from Stop canceled and/or Stop completed.
Once this step is done, you will have to attach your proof of delivery from Options > Attach proof of delivery.
Here you can enable or disable the proofs that you want to send*.
From here, all customers who have their email correctly added will receive an communication that their stop has been completed/canceled with their respective proof attached.
*If you want to create custom fields in your proof of delivery, visit the following article.