Is there a report I can run that shows the last time an invoice was sent?

I understand that you're looking to find out the last time an invoice was sent, @ksottile. While there's not a specific report that gives this information directly, I want to assure you that there's a way to track it using the Audit Log. I’ll be more than happy to guide you through the steps to access this information.

The Audit Log in QuickBooks works like a detailed journal. It keeps a record of every sign-in, any tweaks to settings, and changes about customers, vendors, and employees. It also tracks all the payroll submissions. 
 

To get started, let's go to the Audit log. 
 

1. From the Gear icon, select Audit log.
2. Filter the fields for the User, Date, and Events.
3. Locate the invoice on the list.
4. To open it, click View under the History column.
   
   

    

To get a better idea of how this feature works, you can check out this article: Use the audit log in QuickBooks Online. It explains everything about how to use it and why it’s helpful for keeping track of things in QuickBooks.

In the event you want to pull a report for all unpaid invoices in the future, these steps will guide you.

1. Go to the Reports menu.
2. Enter Open Invoices in the search bar.
3. Select Open Invoices. 
4. Switch to Classic view and customize filters.
5. Once done, click Run report.
    

If you have any questions or thoughts about using the Audit Log or running an invoice report, please don't hesitate to comment below. I’m here to help and would love to hear from you. Your feedback is important to me.