I’m no able o preview invoices on the app.

I can provide other ways to preview your invoices using your mobile, Douglas.

Mobile applications often have limited functionalities compared to their web-based counterparts due to their interface design.That said, we're unable to preview invoices within the QBO application on mobile devices.

As a workaround, we can access QBO via a web browser on your mobile phone to open and preview invoices.

To preview invoices on a web browser, see these steps below:

1. Open this link: https://qbo.intuit.com on your mobile browser.

2. After that, click on the Invoice section under the Sales tab.

3. Choose one invoice, and click on View/Edit under the Action column.

4 Press on the Print or Preview option.

If you want tips on how to send reminders to customers about overdue invoices, you can read this article: Send invoice reminders automatically or manually in QBO.

In the event you need to tie up your client's payment over their invoices, here are the detailed steps you can follow: Record invoice payments in QuickBooks Online.

If you need assistance while working on your sales transaction in QBO, please seek help from the Community. Support will be provided to ensure that all issues are resolved.