Hey @Qlil.

There are two ways you can check if your customer received a copy of the invoice. Let me guide you through each way.

If you want to view multiple customers at a time, you can filter your transactions on All Sales page. Here's how:

1. On the left panel, hover your mouse on Sales, and click on All Sales.
2. Under the Filter drop-down, choose the Type, Status, Delivery Method, Date, and Customer. Then click on Apply.
3. Click on the Status column to categorize then in ascending or descending order.

You will then see the status of the invoices. See screenshot for your visual reference.

However, if you want to view a specific transaction, please follow these steps:

1. Open the invoice. 
2. Scroll down to see the Activities box.

You'll see if your customer viewed the invoice. Check the screenshot below.

Moving forward, you can send yourself a copy of your transactions by going to your Accounts and Settings. Here are the steps:

1. Click on the Gear icon, choose Accounts and Settings.
2. Click on the Sales tab.
3. Under Messages, tick on Email me a copy, click on Save.

Feel free to let us know if you have any other concerns. We'll be delighted to assist you.