How do I link a customer invoice to a project AFTER the invoice is already issued?

Hello there, @kathy-burns.

I can help you link the customer invoice to a project in QuickBooks Online (QBO).

We can simply change the name of the customer on the invoice to the project name. This way, we'll be able to link it to the project. Here's how:

1. Open the existing invoice.
2. Under the Invoice number, click the Customer drop-down arrow.
   
3. Choose the project name.
   
4. Once done, click Save and close.

When you check on the Transactions tab of the Project page, you will see the invoice there. You can check the screenshots I've attached.

You can check these recommended articles for more information about projects:

• Projects FAQs.
• QuickBooks Online Projects.

If you have other questions or need further assistance, just let me know. I’ll be right back to help you more.

I followed steps 1-4 above and when I saved, the entire body of the invoice was erased.  It is linked to an estimate, so I successfully saved the estimate to the project and tried again, but got the same result.

I followed steps 1 - 4 and when I saved to the project number, the entire body of the invoice was erased.  It is linked to an estimate, so I successfully saved the estimate to the project and tried again but got the same result.

Thanks for letting us know what you've done so far, @kathy-burns.

You're on the right track following the steps given by my peer above. Let's perform a few more steps so we can successfully link your invoice to a project in QuickBooks Online (QBO).

To begin with, let's make sure that the project is still under the name of the customer. This way, it will link to your invoice. Here's how to verify it:

1. Go to the Projects menu at the left pane.
2. Look for and open a project you want to associate with a certain invoice. The customer project name should match with the name to your invoice so it will link.

Once done, follow the steps given by my colleague @Maybelle_S. 

Also, here's a great article that you can read through for more insights on how to manage your projects well in QBO. The commonly-asked questions contained in this resource will clarify things like how you're able to budget or delete your project, etc.: Projects Commonly-asked questions in QBO.

Hit the Reply button if you need more with linking your invoice to a project. I'd be glad to assist you further. Wishing you and your business a continued success.