Hello there, @inkexplosion.

We already received reports from other customers about this error in QuickBooks Online. Our engineers are working to fix this as soon as possible.

I suggest reaching out to our Customer Support team so they can collect your account information in a secure environment. Please provide this investigation number INV-38569 so that you will be added as one of the affected users. You'll be able to receive an update about it as they become available.

Here's how to contact our customer support:

1. Log in to your QuickBooks account.
2. Select Help (?) at the top right.
3. Click Contact Us to connect with a live support agent.
4. Enter your concern, then click Let's talk.
5. Choose a way to connect with them.

For more insights about creating invoices, you can read this article: Create an invoice.

Please let me know in the comment section how it goes. I'll be around to help. Have a good day!