Yes, we can create a custom field for your invoice and manually enter the EIN, @tinman0530. I will show you how to achieve this process.
With QuickBooks Online (QBO) Essentials and Plus, you can add up to three custom fields to your sales forms, which will be displayed on the printed versions of your chosen forms. If you have the Advanced version, you can create up to twelve custom fields.
- Navigate to the Gear icon, then Custom fields.
- Click the Add field button and enter a name for the new field.
- Select a form where you want the field to appear.
- Toggle on the Print on form option to ensure it shows up in the printed version.
- Save your changes once you're finished.

Once done, you can create your invoice and manually input the EIN in the designated field.
I also recommend checking this article for guidance on managing transactions after receiving customer payments: Record an invoice payment.
Additionally, to enhance your QuickBooks experience, consider collaborating with our QuickBooks Live Expert Assisted team. These experts specialize in helping you effectively manage your invoices.
If you have further questions about invoices or the custom field feature in QuickBooks, please don't hesitate to reach out. I'll get back to you promptly.