We use a different application to invoice our clients. How do I enter an invoice in quickbooks online to a customer without sending?

Which third party app do you use for invoices?

Sage Timeslips

Recording invoices in QuickBooks Online (QBO) is easy peasy, @belliott-mcswain.

When you record invoices in QBO, you have the option to select Save and Close, Save and Send, or Save and New. Since you're using a different app to send invoices to your clients, you can select the Save and Close option to record the invoices in QBO. This will list the invoices under the customer and receive the payment once they pay for it. I'll attach a screenshot below for your visual reference.

You might also want to view all your recorded sales transactions in QBO. You can go to the Sales menu and select All Sales. From there, you can see the list of all individual transactions created.

If you have further questions on recording invoices in QBO, feel free to leave a comment below. I'm still open to your replies, @belliott-mcswain.

Appreciate the info. Thank you for the tip.

@belliott-mcswain 

We have yet to find any connector to integrate both apps. You may prepare your Receive Payments data with the following template

then utilize an importer tool

https://transactionpro.grsm.io/qbo