What has to be considered regarding the PCI-DSS level?

The PCI-DSS compliance level is different, respective the way you are integrating billwerk in the checkout process:

1. When you are using the billwerk generated and hosted self service signup page or the billwerk payment form (inside an iFrame): SAQ A
2. When you are using billwerkJS for you own checkout page: SAQ A-EP

Very important: billwerk and your system is not allowed to received, store and transfer any credit card data! The transmission of the data is done directly out of the browser to the PSP. 

You can find further information regarding PCI-DSS here: https://www.pcisecuritystandards.org/