Hello, @JeffT229. 

Welcome to the Community. Let me help you with your invoice concerns in QuickBooks.

Currently, the option to send a receipt for your paid invoices in QuickBooks Online is unavailable. For now, you can go to the Invoice page and then send the paid invoice from there. Let me guide you how.

1. From the left menu, click Sales.
2. Choose the Invoices tab.
3. Find the invoice that marked as paid.
4. Under the Actions column, click the drop-down and select Send.
5. Enter the email address under TO section.
6. Click Send.

Aside from sending the paid invoice, you can also let your customers know their invoices are paid, you can accomplish this by hand.

Here's how:

1. Highlight the Sales tab, then select All Sales.
2. On the Filter drop-down menu, click it.
3. Select Money received under the Type drop-down menu, then tap Apply.
4. Locate the Payment transactions that you want to send to your customers, then click any 1 of them.
5. Hit the Print menu. On the Print preview screen, download the PDF copy of the receipt. You can do this on multiple receipts so you can attach the PDF files to your own email and send it to the appropriate client.

You can use the workaround I suggested above until a new feature becomes available.

Additionally, you can read this article for your reference: Email or print multiple invoices and sales forms.

Fill me in if you have additional questions about your invoices in QuickBooks. I'm always willing to assist. Take care always.