Full editing rights to invoices

When a line is added to an invoice that has already been paid if that line can be saved to the invoice than it should also be able to be deleted,(for example, an invoice has been unlocked to add a surcharge with payment and left unlocked), but instead it allows you to save the added line and when you try and delete the incorrect line it pops up saying changes can not be made as payment has has been offset.

It also does not allow you to have an invoice that is paid in installments that has two or more payments  that require a surcharge added (credit card). You only have the option to add the surcharge once before the first payment.

There should so be the option to enter a flat amount as well as a percentage for the surcharge, eg 1.7% or $0.50.

The ability to fully edit invoices, payments etc should be an option. Obviously this option would not be available to everyone in an organisation but it should be available for one (1) or two (2) people in each organisation and that should be up to each organisation.

It does not look good having credit notes every time you need to make an adjustment.