I'm here to share some information on how importing your invoices works in QuickBooks.
When importing your invoices, there is a specific file format or required columns to be included. I've added a screenshot of the sample file for your reference.
Following the required format enables you to map your invoice details with the QuickBooks fields during the importing process.
Once you have successfully imported your invoice, you can open each invoice and manually add the bank or payment instruction in the Message box. You can read through this article for more detailed steps about this process: Import multiple invoices at once.
I've added these articles as additional reference in managing your invoices and other sales forms:
On my custom Invoice form, I am able to include bank instructions in the message box. When I import invoices, I lose the ability to include this message.
Thanks for adding more details about your concern, BL16.
As mentioned by my colleague, there is a specific file format when importing invoices. We're unable to include the bank message since there's no field to add it to the template.
You can consider using a third-party application to help achieve this customization. Let’s go to the App Center to find one. From there, you’ll get a better comparison of these apps and see if one meets your need.