Convenience fees are a great way to push the cost of the software directly onto the end users. This could be used selectively and just be applied to people receiving parking tickets, or you can set various fees for any aspect of the offerings, term permits, temp permits, and violations and the related online payments.
The one thing you can’t do is fail to identify that there are additional fees in play when using the App, QR Code, etc…
Several big parking entities have now been sued for failing to properly identify these fees in their signage and pricing, with Metropolis being the most recent settled case. This is easily avoidable, so be sure to produce accurate signage.