Hi, @Annie Tang ,
According to your title, I assume you are handling a SharePoint 2013 farm and try to get a automated solution for the whole process, please correct me if this is not your scenario.
In short words, we do not have a good solution with out-of-box ways for you task.
Using REST API, we can send http request from Platform 2013 workflow to remove permissions on list/library/item. This is practicable. The point is that we want to remove the permission after all the accountants have downloaded and submitted files. In workflow we do not have triggers monitoring such events. We will need some one to manually run the workflow to remove the permission after he/she confirms that all the files have been sent. This is far from a perfect solution as it is not much different from finishing the process manually from UI.
You may need to find some 3rd party tools or create custom solutions for this.
Reference for REST API if you are interested about it:
https://sharepoint.stackexchange.com/questions/154232/break-role-inheritance-and-assign-permissions-to-document-with-rest-api
https://learn.microsoft.com/en-us/previous-versions/office/developer/sharepoint-rest-reference/dn531432(v=office.15)
https://learn.microsoft.com/en-us/sharepoint/dev/sp-add-ins/set-custom-permissions-on-a-list-by-using-the-rest-interface?redirectedfrom=MSDN
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