You can duplicate a customer in Moon Invoice easily by following the steps below.

1. Open the Moon Invoice application on your device or tap on this link.
2. From the main menu on your left, go to Sales ➜ Customer.
3. Click the ‘+’ icon to create a customer or select an existing one that you want.
4. On the right-hand side, click on the three-dot icon (⋮) and select Duplicate, then choose Customer. 
5. It will automatically create a duplicate customer on your left-hand side.