How to create a credit note for a customer? This option doesn't appear in my QuickBooks APP?

Thank you for visiting the QuickBooks Community, annalisa. I'll be providing details on how credit note works in QuickBooks Online. Let me also ensure you can create this entry on the program.

Please know that recording a credit note for a customer in QBO is currently unavailable in the QuickBooks mobile app. This is why this doesn't appear on your end. 

I recommend accessing your QuickBooks account via a regular browser. This way, you're able to create the said entry by going to the + New button. Then, follow the steps below.

1. Choose Credit note under the Customer column.
2. From the Customer dropdown, select the customer's name.
3. Enter the credit note details, such as the date and the amount. Tip: You can create a custom credit service item so you can quickly add it to credit notes as a single line item.
4. When you're done, click Save and close.

After that, you can refer to this article in case you need steps on how to apply the credit note to an existing invoice: Create and apply credit notes or delayed credits in QuickBooks Online.

Lastly, you can read this article on how you can view, create, and edit sales transactions from within the Sales page: View sales transactions in QuickBooks Online.

If you have additional questions about credit note on the program, please don't hesitate to leave a message in the comment section. I'm always around here in the Community to help, annalisa. Have a great day.