Who these guides are for
People who send their own invoices: freelancers, sole traders, contractors and small teams. No accounting background is assumed, and nothing here is written for a tax adviser.
Every legal claim names the paragraph it comes from — §14 UStG in Germany, §11 UStG 1994 in Austria, Article 226 of the EU VAT Directive across the union — so you can check it instead of taking our word for it. This is tooling, not tax advice; your accountant settles the edge cases.
Where to start
Four guides. Which one you need depends on what is in front of you right now.
- You are writing your first invoice. Start with the freelancer guide: what has to appear on the document, what changes if you are a sole trader or a contractor, and how to word the payment terms.
- The numbering worries you. The invoice numbering guide covers the gap-free sequence the law wants, what a valid number looks like, and how to run more than one series without breaking either.
- You are doing it in a spreadsheet. The Excel guide walks both routes, from a template and from scratch, with the formulas — and says plainly which part a spreadsheet cannot do for you.
- You invoice into another country. The country guides cover what that country requires on the document, which tax rules apply, and what its e-invoicing mandate changes.
Why none of these carries a date
Invoice rules move. Germany's e-invoicing dates, VAT rates and the small-business thresholds have all changed in the last few years, and they will change again.
So these are maintained references rather than posts. A guide is corrected in place when the law moves, which is why no entry above shows a publication date: the date would tell you when it was written, not whether it is still right.
Where a claim rests on a statute or a ministry page, the guide links the source at the foot so you can read it yourself.