Hi, Susan. Currently, QuickBooks Online doesn’t have the functionality to add a location field next to the invoice number in the subject line when emailing invoices. However, you can manually enter the location identifier into the subject line before sending the email to your customer.
You can also explore using Custom Form Styles to tweak what information is included directly in the invoice itself. This allows you to add details like the location identifier to the invoice, ensuring all necessary information is visible when shared with your customers.
If you have additional questions, feel free to comment them on the thread. We'll gladly loop back to assist you.