Thanks for joining us here in the Community, info-50fiftythea.
You've come to the right place for assistance. I'm happy to provide info about adding custom fields to invoices in QuickBooks Online.
You can create 3 custom fields on sales forms in QuickBooks Online Plus and Essentials. Here's how:
1. Go to Settings ⚙ and select Custom fields.
2. Select Add field. (Note: If this is your first time creating a custom field, select Add custom field.)
3. Enter a name in the Name field.
4. Select the All Sales forms or Purchase Order checkbox. Or, select both.
5. (Optional) To show the custom field on printed and delivered forms, turn on Print on form. Otherwise, it’ll only appear in QuickBooks Online.
6. Click Save.
The following article provides additional info about adding custom fields to sales forms and purchase orders in QuickBooks Online.
Please don't hesitate to drop a comment below if you have any other questions. I'll be here to lend a hand.