How can I include the number of days that an invoice is overdue into an automated reminder email?

Hello there, lamancha-carpet.

The option to include the number of days of overdue invoices is currently unavailable. However, I've got a workaround you may consider doing. You can utilize the Email message to add the value that a client's invoices are overdue. Please see the screenshot below:

Keep me posted if you need anything else.