In germany it is very common to rise dunning fees or give early payment discounts (skonto).

example:

dunning fee: if the invoice isnt payed after 30 days net add fee of 7.87% per a (or 4,87%)

Process: Refund Invoice -> Create new one with referral to old one + the information of invalidity of the old one. The "payment follow up" Module is kind of unsatisfying, because you are not able to rise any fees.

early payment discounts: if payed within 7 days after billing, but with a payment target of 30 days, the customer gets 4% discount

Process: Register full payment -> do the accounting record the other way around -> subtract or add taxes etc. [additional_discount] (www.openerp.com/apps/trunk/additional_discount/) is just for 6.1.

But still both are feasible, but we are at the domain of ERP (as automated as possible) so this isnt a very satisfying solution.

Is there a more simple solution like an app or module to solve this? How do other companies solve this problem, but of preventing both to happen? Is there an easy solution in v8?

If there is no solution i am thinging about to raise a fund at [bountysource.com] (www.bountysource.com) and do it my self. Do you think that this topic could be interesting enough?