When your customers reply to the Invoice you've sent through email, their reply will go to the Customer-facing email address that you've set up in your QuickBooks Online account, Sovay.

This email can be your company email or a different email address. To check or change this email address, please follow the steps below:

1. Click the Gear icon in QuickBooks Online.
2. Select Account and Settings.
3. Go to the Company tab.
4. In the Contact info section, click the Pencil icon to edit.
5. Update the Customer-facing email field.
6. Click Save and then Done.

Once you've checked your customer's reply and they've paid their invoices, please refer to this article to learn how to record it: Record invoice payments in QuickBooks Online.

Let me know if you need further assistance locating your customer's response. Keep safe.