Hello, bweiss.
The way to add another subject field in the email section of the invoice is unavailable. You have the option to set your greetings using the customer's company name. Let me show you how:
- Go to the Gear icon and select Custom form styles.
- Select an existing invoice template or click New style at the upper-right.
- Click the Email tab and select the Standard email section.
- Check the Use greeting box and select your preference.
- Click Done.
However, if you're referring to adding fields within the invoice, you can use this link for more details: Customize invoices, estimates, and sales receipts in QuickBooks Online.
Let me know if you have other questions. Have a great day!
