How do you change a project from an existing parent customer to an existing sub customer?

I'm here to guide you as to how you can change a project from the parent customer to a sub-customer in QuickBooks Online (QBO), @ELM tree.

For the time being, you're unable to edit a project to change its existing customer. However, you can move your transactions to another project, customer, or sub-customer.

With this, you'll first have to set up a new project for your existing sub-customer. Then, move the project transactions from the parent customer to the sub-customer. After that, you may opt to delete the project for the existing parent customer to keep your list updated.

To move expense transactions from the parent customer's project, you'll have to find and open each of them and select the appropriate sub-customers project. Do this for each expense item you want to add to your project. Please see the screenshot below for your reference.

On the other hand, adding an existing project invoice to another project require a little caution before you can edit them. For the complete details, please refer to this article: Add existing invoices to QuickBooks Online Projects.

Also, to answer the most frequently asked questions about Projects and how you can use it to quickly calculate your project income and costs in QBO, I'd recommend checking out this article: 

• Projects FAQ
• Track income, costs, and profitability by project

Please don't hesitate to let me know in the comments if you have other project concerns and questions about managing transactions in QBO. I'll gladly help. Take care, and I wish you continued success, @ELM tree.