I just released FatturaElettronica .NET v3.6.3. Since version 3.6.1, the project has added English to the list of supported languages. The latest release improves English support, aligning it with the official translation. Michael Mairegger contributed this improvement.
The Fattura Elettronica open-source project allows for the validation and de/serialization of electronic invoices that adhere to the standard defined by the Italian Revenue Agency.