You can easily create a credit note against an Invoice in Moon Invoice by following the steps below:

1. Open the Moon Invoice application on your device or tap on this link.
2. Navigate to the Sales → Invoice.
3. Now, select an existing invoice for which you want to create a credit note, then click on three dots (⋮) → Credit Notes → Create New.
4. Now, verify the details and click on save to create a credit note against an Invoice.