Additional Billing Informations
The support told me there is no way to add extra Information to invoices. This is pretty bad, because I need to add legal details for a valid invoice here in germany.
Update:
It is apparently not possible to store payment information in an invoice. However, information about which account the payment should be made to is essential. Here too, a permissible outgoing invoice is not possible under German law. It really shouldn't be a hurdle to print this information! The ultimate solution would be simple e-payment via PayPal or photo transfer (via QR code).
I don't want to be forced to export and use another solution like Xero etc. I wan't to be able to create a valid invoice for my customers.

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Darragh Gamble commented
As we are only 2 months into Atera I was astonished that we cannot add our payment terms to invoices. We do not integrate into Xero or Quickbooks . As it stands without our payment terms on the invoice we cannot use Atera for billing which is a real disappointment. Cant be that difficult surely ?
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COOLNETAU commented
I have been told, but am not sure, that invoices that are sent to Xero (as an example) do not get sent via Atera - they just end up as a draft in xero
It means that you can send your invoice from xero with all of the payment details etc.
I am yet to integrate this, however will be looking at this soon