We have a third party customer (global_name) that has requested that we send all invoices to their processing firm and take out a 3% fee off of every invoice (including taxes). I am struggling to come up with a solution and have a few questions regarding this situation and billing.

1. I know there are a lot of complex settings we have not used yet regarding billing with fees and adjustments. I was looking into Billing Configurable Financials. We don't have one set up, but was wondering if I could utilize this functionality for what I am trying to accomplish or something like this?

2. I am not seeing a method to calculate a fee in a way that includes taxes. We use a Vertex API Integration to make a call and stick it onto special charges. Is there a way to calculate a fee that would include special charges, really just a way to calculate a fee based on the invoice total plus taxes?

3. Is there a way to put a fee against a total invoice, instead of on each individual line?

4. Is there a way that updates to voucher detail lines would translate back to the request and update it to match (potentially an insert to both tables, or adding the charge as it goes to voucher to each line?