I don't have the option to add an existing invoice to a project. I didn't have this issue until last week. I am unable to edit invoices and change customers to projects.

Let me help you get past this issue, Ashley.

A cache-related problem is likely causing the inability to add an existing invoice to a project. If this is the case, let's perform some troubleshooting steps. We can use a private or incognito window to rule this out in your browser. Here are the shortcut keys:

• For Mozilla Firefox browser: Ctrl + Shift + P
• For Google Chrome browser: Ctrl + Shift + N
• For Safari browser: Command + Shift + N

Next, log in to your QuickBooks Online (QBO) account and do your task again. If it works, clear your browser's cache. This removes the webpage data that's causing the situation. If a private browser doesn't work, use other installed supported browsers as an alternative. 

Moreover, here's an article that you can use as a reference in managing your projects better: Create and manage projects in QuickBooks Online. 

In case you want to add, delete, or restore a class, check out this article for more guidance: Create and manage classes in QuickBooks Online.

Please let me know if you require further assistance by leaving a reply below. Our main priority is to ensure that you have a seamless experience. Stay safe!

That is not the issue. A project has been created and I cannot edit the invoice to change to the project. It won't even give me the option. 

I appreciate you for clarifying your concern, Ashley. Let me guide you on how to edit invoices and change customers to projects. 

Just a quick heads-up when you're editing invoices linked to payments - be careful as it can disconnect the amount. It's best to add existing invoices to projects before you associate them with a payment.

Here are the steps to add an unpaid invoice:

1. Navigate to Sales and select Invoices.

2. Locate and choose the unpaid invoice.

3. Click Edit invoice.

4. Pick the project from the Customer dropdown.

5. Finally, hit Save.

To add paid invoices to your project, refer to this article for the steps: Add existing invoices to projects in QuickBooks Online.

If you're still unable to find the option and complete your task, you can contact our support team for further assistance.

In case you want to utilize projects to keep tabs on your labor costs and profitability, check out this article for more guidance: Track hourly labor costs and profitability by project in QuickBooks Online.

I'm still ready to back you up if you have any other concerns besides adding existing invoices to a project. Feel at ease to share them here in the Community. Stay safe!