I'm creating a statement for a customer that has several subcustomers, but some overdue invoices from subcustomers are not showing. Yes I've checked the date.

Hi WildPepperIsle, 

We can check the set up of your sub-customer if bill with parent is selected. 

Here's how: 

1. On Sales tab select Customers.
2. Select a sub-customer not showing on the statement. 
3. On Is sub-customer section, make sure that Bill with parent is selected. 
4. Then, click Save. 

Once done, you can try to create a statement to confirm if it shows now the overdue invoices of the sub-customer.

Feel free to check on this article: Create and send customer statements in QuickBooks Online. 

Let us know if you need further assistance. Have a nice day.