Does QB online Keep history of when an invoice was emailed to a customer?

Hello there.

I appreciate you for posting your question here in the Community space. Yes, QuickBooks Online keeps the activity history of your invoices, whether it's sent, viewed, or paid by your customers.

I'll show you how to find this by following the steps below:

1. Open QuickBooks Online.
2. On the left menu, head to Sales and choose Invoices.
3. Find and select the invoice you want to view history.

I've provided a screenshot below for a better view.

Furthermore, you can also consider using QuickBooks Payments to process payments and record them automatically. Otherwise, you can manually record an invoice payment in QBO. 

Feel free to drop by if you have any other concerns besides the invoice activity history. I'd gladly help you anytime.