How to hide amount paid on purchase invoice, and amount credited on sales invoice
Why would you want to do this?
For example if I have to correct an invoice already issued that meanwhile has been paid without changing the date.
That situation would, in my opinion, reinforce the desire to show amounts paid/credited, not negate it. There is certainly no risk of misunderstanding within Manager, and purchase invoices are not sent to suppliers. So the only circumstance this might apply to is a sales invoice sent to a customer. Without showing what has already been credited, such a document could easily be misinterpreted as an additional demand for payment.
I agree with Tut.