Can I create a statement for only a project, under a parent client?

Good to see you here in the Community, rockinraerenee.

Yes, you can create a statement for one project under a parent client in QuickBooks Online. Please be reminded that the statement will show the client's total open balance regardless if you filter its date for one project.

Here's how to create a statement for one project:
 

1. Go to Customers.
2. Locate your client's name and click Create statement.
   
3. Filter the statement date and hit Apply.
   
4. You can Print or Preview the statement.
   
5. You'll see the invoice and payment from the print or preview screen including the client's total open balance.
   

To know more about how statements work in QuickBooks Online, you can refer to this article: Create and send customer statements in QuickBooks Online. It contains information on what options you can include in your customer statements.

I appreciate your time working with us. If there's anything else I can help you with or other QuickBooks concerns, please let me know in the comment section. I'm always here to help. Have a lovely day!

I am looking for the same thing.  I have a customer and we have two large projects going for them.  They are wanting to close out one project and I need to send them a statement for that project showing all open invoices (all retention still owing and current unpaid invoices) and a balance owing on that specific project.   I would even settle for a customer statement that shows all projects, but AT LEAST shows which project each invoice applies to. There is no way to send a statement to a customer that they can see at a glance what is still owing on a project.  QB Desktop had this functionality.

I have found a workaround that may be helpful. 

Go into the project, click on transactions.

Filter - all invoices or open invoices, whatever you need

Filter - date for all time, or your required date range.

This should produce the information usually included on a statement. 

Then I exported to excel, gave it a title, added my logo, add/delete anything I need/don't want.  (I actually opened the file in numbers not excel, but whatever you work with).

Export to PDF and email to the client.

I feel like customer statements that can be broken out by project is a vital feature that was included in Desktop, but hopefully this can help someone who needs the information right now until they get it integrated into QBO (which will probably be never, based on the fact that people have been asking for this for almost 3 years now and we've got crickets.)