I am currently working on a banking site. We are designing a section of the site where users can follow their applications, i.e. for a loan. They can sign and upload documents from there.
There will be a list of documents to provide. For instance their ID, proof of address, proof of income etc. For each type of document, they can upload several files if needed.
Imagine they click on Proof of income, they will be prompted a modal window with some guidelines and an upload area. Once they have finished adding the necessary file, they will have to press a "send" button. Once it's sent, they cannot change those files or replace them. This is a technical constraint.
According to you, how should we handle errors? If one of the files is too big, we will signify it appropriately, but should we force the user to delete that file or replace it so that the modal is clear of any error message before sending?
Or should we let the user see the error message, add a different file while leaving that error message visible on the page, and sending the whole thing with the error message still displayed?
Thanks for your help