Hi @Sarloubra. Are you using QuickBooks Payments or PayPal? Once either one is connected to QuickBooks Online (QBO), your customer will see a "Pay Invoice" link when they receive the invoice.
To keep this from showing, follow these steps:
1. For PayPal: Go to the integrations page and disconnect it.

2. For QuickBooks Payments: Turn it off in your invoice settings.

Let us know if you have further questions or concern.