Here in the UK the customer are against the law to pass any of theses on to the customer, maybe other parts of the world its fine but this would get to confusing for @wrongecho to manage depending on what part of the world you are in.
Personally i say you would need to world to work out the what your card fee is and add it as a different product to the invoice.
We personally be using stripe in the portal but our accounting system we use free agent and we use Tyl by Natwest for our card payments.
