Accountants hold more sensitive information about a client than almost anybody else the client deals with, and they hold it for years. That makes the security question for a portal less about the vendor's certifications and more about how the firm runs it day to day. A secure client portal for accountants is one whose ordinary controls are usable by whoever in the practice actually administers software, because a control that requires a support ticket is a control that will not be used in the week it matters.
The staff side is the bigger exposure
A client login sees one client. A staff login sees the book. So the controls that matter most are the internal ones: individual accounts for every member of staff, a second authentication factor you can require rather than suggest, and the ability to remove somebody's access completely on the day they leave rather than the week after. Seasonal and temporary staff make this a live issue for most firms every year.
Know who currently has a door into the firm
Access accumulates quietly. A bookkeeper added for one job, a client contact who moved on, a former client whose engagement ended two years ago. Ask to see the single screen that lists everybody with access right now and what they can reach. If that screen does not exist, nobody in the firm can answer the question, which means the answer is worse than you think.
What the software cannot decide for you
How long you retain client records, what you must do if something goes wrong, and what your professional obligations are in your jurisdiction are matters for your regulator, your professional body and your own advisers. Software can enforce a retention period once you have chosen one and can give you a log to reason from. It cannot choose the period, and any vendor implying otherwise is selling reassurance rather than a control.
Questions people ask about secure client portal for accountants
Should clients be required to use multi factor authentication?
Requiring it for staff is close to unarguable. Requiring it for clients raises security and lowers adoption, so many firms offer it, encourage it, and require it only where the client relationship makes that easy.
Is a portal inside our tax software secure enough?
Test it against the same checks: individual accounts, removable access, a second factor, a readable log. Bundled portals are not less secure by nature, but they often have coarser permissions.
How long should client documents stay in the portal?
As long as your retention policy says and no longer. Decide the policy with your own adviser, then configure the system to apply it, so retention is not a series of individual decisions.