> Every invoice—whether B2B or even B2C (receipts included)—must be sent electronically using a government-defined XML format

So not a universal standard then. Imagine having to implement a different format for every country you do business with...

For the Netherlands there is a similar (but slightly different I believe) XML type format required if you want to do business with the government. Initially a company successfully lobbied to get their closed-specification version to be the mandated standard for government, to get the XML spec you had to become partner (I believe for €8k/year or something).

Luckily they are now performing a XKCD 927 and have defined a few new (this time open) standards, which they aim to consolidate into a new spec that complies to EN 16931. EN 16931 is the EU compliance standard for e-invoicing.

In New Zealand we are also phasing in eInvoicing using Peppol BIS 3.0, which complies to EN 16931.