I appreciate you for returning to this thread, @Kazsnafix. 

Although QuickBooks Online (QBO) doesn't have the reminders feature like in the QuickBooks Desktop (QBDT), I can suggest an alternative closer to your specifications.

When you choose to log in to your client's company, you can consider utilizing the Tasks feature in QBO to see overdue and upcoming invoices and bills. Depending on which experience your client is, you can see from the Tasks section or page the overdue and upcoming invoices and bills. You can also see reminders for certain types of recurring transactions in this feature.  

Here's how you can utilize the feature if it's within the new Home experience:

1. Select Go to QuickBooks in your ProAdvisor account and select your client's company.
2. Go to Dashboard in your clients QBO company.
3. Select Customize layout. Then, Add or remove widgets.
4. Ensure that Tasks is placed with a checkmark.
5. Scroll down and find the Tasks section. Then, move it around to place the section somewhere more visible.
6. Hit Save.

If you're in the old experience, simply select Tasks in the left navigation panel. I've attached a screenshot for visual reference. 

As for the Print Checks, you will have to manually check for this one.

In QBO, you can save time on tracking and recording receipts from vendors. Let me add this article as a future reference: Upload your receipts to QuickBooks Online. 

Keep us posted if you need further assistance navigating QBO's Tasks feature. We'll do our best to assist.