How do I look up a paid Invoice

Good to see you here in the Community, @winnkoh.

I can help locate the paid invoices in QuickBooks Online (QBO). We can do that by going to the Sales tab.

Here's how:

1. Go to the Sales menu.
2. Click Invoices.
3. Select the Status drop-down arrow, then choose Paid.
   

In addition, I've collected these articles for reference. These contain complete details on how to record a refund, void, and manage your invoice efficiently: 

• Record a customer refund in QuickBooks Online
• Void or refund customer payments in QuickBooks Online 
• View sales transactions

Let me know if you have other questions about invoices in QuickBooks? You can leave the details in your reply, and I'll get back to you. I'll also answer other QuickBooks concerns you may have. Have a great day.