How can I add refund button to invoices or make the button visible?

Hi there. 

I recognize the convenience of having a refund button in our Invoice window.  

Currently, this feature isn't available in QuickBooks Online (QBO). However, we would love to hear your ideas about having this feature and recommend you submit feedback. This way, we can enhance your experience with QBO, and your feature suggestion will be shared with our Product Development Team.

Here's how:  

1. Select the Gear icon, then choose Feedback.
2. Enter your comments or product suggestions.
3. Select Next to submit.

You can visit this article to learn how to process your customer's returned payments in QBO: Record a customer refund in QuickBooks Online. 

Moreover, I'll add this article about personalizing your sales forms: Customize invoices, estimates, and sales receipts in QuickBooks Online. 

If you have any other questions regarding managing your invoices, please don't hesitate to comment below. Stay safe!