DOKKA offers a confidential workspace, which allows to upload confidential documents (such as salary / payroll information).
All accountants / bookkeepers which are connected to a certain company can access the confidential workspace. You can define which clients has access to information in this folder by assigning them as Confidential Users, as explained here.
Uploading files to this folder is done by sending documents to a unique email address, which you can see in the header of the Confidential Workspace (just below the company name).
The format of the email address is "company name DOT confidential". For example - CompanyName.email@example.com