If I come across one more inconstant data modal that is undocumented in this project am I going to get significantly annoyed!!!!!!!!!!

Have you tried EDI?

@GieltjE have not herd of that one

It's a "standard" for digital invoicing, every industry has one, a lot of countries have one. Every standard has shitloads of sub standard. Every standard has a few hundred pages of documentation and usualy is incompatible with every other one.

To make it worse there is no logical structure if you haven't read the entire documentation (after reading it you'll want to murder the inventor and everyone who believes it was a acceptable decision in any sense)