Okay, I'll have a look at the Signup email -- this will be okay for all but local (Austrian) residents (so good I'm not not based in Germany, as then it would mean I would have to go the hard way for 75% of my customers).
However what should I do with those people who simply donate but do not sign up? About 25% of my "customers" send money just as a donation so I would need the email to be sent regardless of the people registering or not (well I do know that my case is special, in so far as all payments I receive are 90% regarded as donation and only say 10% as actual delivery of a service...)
For Austrian residents I need a digital signature, which for right now I can only add to PDF documents. No approved (by authorities) software to sign a mail exists for right now. I contacted Paypal and read through bout 500 pages of business guides by the chamber of commerce to gather the below information (ain't no place were ebiz info for small companies is layed out in detail regarding to selling services only and to selling most stuff not in your own country):
The Papyal invoice is an invoice by Paypal (not you!!) to your customer notifying him that he paid. It is nothing more and legally not binding for you but for Paypal. The layout choices and text you put on it, are just a service by Paypal to match your corporate design/strategy. So for anyone using s2member inside the European Union, you have to (manually) create a correct invoice additionally to the Paypal invoice.
Depending on legislation this invoice has to be digitally signed. So you have to get a digital signature system that is approved by your countries authorities. For Austria there is only ONE provider that is authorised to sell digital signatures: (
http://www.a-trust.at/ ).
They for example offer a pdf signature creation tool for 69€. Mind this requires Adobe Acrobat (it comes as plugin) AND even worse this requires you to buy a terminal (at least another 100€) that you connect to your PC for verification. So well, overall this will set you back by around 500€ plus installation fees and usage fees of at least 50€/year.
However at least in Austria, the digital signature is only required for sales to Austrian citizens. For sales to other EU member country citizens it is not required. Hence I'll probably save the hassle, and send out paper invoices to all Austrian customers. For other countries a valid invoice is still needed but there is no requirement to have it digitally signed (according to EU law, this only happens once you are liable to charge customers the VAT of their (not your) country, so this depends on the amount of sales per year to that country and can be required from sales 5000€ or higher).
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So what would in effect be really needed in the long term, is an Acrobat plugin (Acrobat is simply the business standard in EU for any invoices) that creates a pdf which then by another plugin can be digitally signed. But for the start having the signup confirmation email sent regardless of whether someone signed up or not, would solve (at least for me) 90% of the trouble.
Besides S2member documentation should warn users to look at local tax laws and ebiz laws a bit. S2member is still a really beginner friendly tool, that many may (as I did in the beginning) just use because it offers a bit more than your simple paypal donate button, then brings you in more business, and suddenly you have to watch out for all that local consumer protection laws, correct disclaimer, Terms of Use, and so on. Noone who uses s2member should be doing so without provdiding sound TOUs and a sound disclaimer - so maybe there should be standard fields to add a link to your TOU and Disclaimer too so users don't forget that.
Personal note:
when I installed s2member, I thought well just another wordpress plugin, but I just start to realise all the paperwork and legal obligations that came with receiving money commercially. It's no wonder that you have loads of startups in the US, but much fewer in EU cause everything is 10x as complicated here.