There's no valid certificate for digital Accessibility and you don'T need one
One of the most frequently asked questions by customers is whether we can certify the accessibility of websites. The short answer - we can't, since there are no corresponding certificates.
Or to put it another way: the determination that a website conforms to WCAG or in Germany to EN 301549 is certification, that's all.
How useful can it be to certify a website? Even authorities nowadays frequently redesign their interface. Content is integrated and removed, modules are exchanged and a lot of content is constantly changing. You might as well certify a newly planted tree.
BITV test is not a certification
The BITV test is not a certification per se. It's an interpretation of WCAG/EN 301549 and has no public legitimacy as it's developed and maintained by private companies - in Germany we say Bock and Gärtner.
WAKA nobody needs
In Austria there is the WAKA certificate. Apparently, the makers were looking for and found a source of money. I didn't find the concept convincing.
VPAT is not suitable for websites
Internationally, the VPAT Voluntary Product Accessibility Template seems to be establishing itself as the standard. It is also not a certificate, but a structured report on the accessibility of a product or software. In my opinion it is too powerful for a content-heavy website, it is more aimed at complex web applications such as Google Docs or Jira. In addition, it is practically unknown in this country, although there is a special version for EN 301549. To my knowledge, there is no German company that offers the creation of a VPAT as a service - apart from us, of course. Think you can create it yourself? Good luck then.
Conclusion: You can't buy anything from a certification
In Germany there is a fanatical love of complex formal processes and weighty papers that say meaningful things like "Certified according to DIN/ISO...". Whether these interest anyone outside the bubble - who cares?
Don't waste your money on formal acknowledgments like this, because they're not useful to you, and the person affected by barriers doesn't care at all. If you have too much money left over, put it in a feedback mechanism.