We run a subscription service and have 3 different payment types throught the life-cycle of an account (Signup/Trial - prepaid by credit card, monthly subscription - paid by direct debit, user add-ons - prepaid by credit card). Each are very different and each needs a very different email template.

I belive defining the email template to be used when email an invoice via the API is critical. Unlike much of the backend work we do which is out of sight of the customer and can often be worked around, the email is customer facing and clear transparent communication with customers is critical to any business. Without customers we have no use for an accounting system, Xero or other.

if someone is doing something as detailed as using an api to get xero to generate an invoice and then send it via emails, they probably need more than one email template...i cant build an app to integrate with xero to autosend emails until this works....please this is essential...

Companies do have multiple Sales Invoice templates.
Having just a default template for a Sales Invoice API is not enough.

Would be really useful to build this feature in.

Yes choosing an email template would be really useful.

It should have been there by default.

Yeah, just found out. Disappointed that this is missing from the API.
We need to send invoices for companies that have either paid already or still need to pay. A different message would be very usefull.