I had a Google Cloud project which I used with a "private" account user@mycompany.com. I wanted to allow my colleagues to the project, too, so I created an organiatzion mycompany.com for Google Identiy.
I wanted to re-use user@mycompany.com and had to delete it because it was a private account and thus blocked for Google Identity as far as I understand. In order to delete it, I switched ownership of the CCP project over to another private account other@mycompany.com.
Then I created the organization mycompany.com and moved the GCP project under its root. Everything runs smoothly, except I can no longer access the billing account which is still associated with the GCP project. I need access to it to download the invoice for the accounting department in my company.
I could replace the account with a new one and it'd be nice if it was configured in the organization rather than associated with a specific account. However, the invoice would probably lost and the accounting team would be in trouble as would I.
I can't use the GCP billing chat support because the first message I get is ~"you're not the admin of the project's billing account" without further options.
The GCP is still using the billing account and the ID is shown.