Where do I put the data I want to show up in the custom fields box when creating an invoice? I want to select the information from each customer.

I'm glad to see you here in the Community, pomonait.

I'm happy to show you how to add custom fields to invoices in QuickBooks Online.

To set up custom fields to appear on invoices, here's what you'll need to do:

1. Click the Gear icon at the top.
2. Select Account and Settings.
3. Click Sales in the left navigation menu.
4. Go to Sales form content section, then click the pencil icon.
5. Enter a Name into each dialogue box beneath the heading Custom fields and select whether you want the field to be internal (only displayed in QuickBooks), or public (displayed in QuickBooks and displayed/printed on sales forms).
6. Click Save.
7. Click Done.

To give you more of an idea about this process, you can check this article: How to add custom fields to invoices.

That's it! Now you're now able to add custom fields to invoices and enter the data you need.

For additional reference, I'm attaching some articles that you may find helpful in the future:

• How to set up custom invoice numbers [Video]
• How to change an invoice number [Video]
• How to email an invoice [Video]
• How to delete an invoice [Video]
• How to set up a recurring invoice for customers

That's it! This will point you in the right direction, pomonait.

You can always get back to me if you have any other follow up questions.  I'm always here to offer additional assistance. Have a wonderful day ahead.