Can I give my accountant a separate log in to my account
Yes - account settings / team management / add a new team member. I think by default new team member logins have access to everything (except the ability to create more logins, that’s reserved just for the primary admin) but you can lock down certain areas if you wish.
Edit: P.S. if you have two factor authentication enabled then you’ll need to set that up for the accountant too, and they’ll need the Google Authenticator app to be able to log in.
@ian_roberts is correct. However, if your accountant is managing several QuickFile accounts, I’d recommend they have a look at Affinity, which is aimed at accountants