When creating a sub-customer, you have the option to select the parent billing account. This allows you to enter charges for both the parent customer and the sub-customer, ensuring that both charges appear on the same invoice, @evinna.

To do this, make sure to select the "Bill parent customer" option in the sub-customer profile.

Here's how:

1. Go to Sales from the left menu, then Customers.
2. Find and open the sub-customer's profile.
3. Click Edit.
   
4. Tick the Is sub-customer box.
5. Enter the parent customer, and then select Bill parent customer.
6. Click Save.
   

Once completed, you can create an invoice for the sub-customer by clicking the New button and selecting Invoice.

Check out this link for more information about creating invoices for a parent customer and its sub-customers  in QuickBooks Online.

QuickBooks also provides a link that allows you to customize reports to display a list of invoices due on a specific date. 

By following the steps outlined above, you can ensure that the invoices reflect your chosen billing option for the parent customer. If you need further assistance managing parent customers. We're always here to help you.