In the Accounting preview, which only Magpie administrators can open, an admin can add an accountant by the email address of their Magpie account, on the team's Members page or in Accounting settings. The accountant can open everything in Accounting and nothing else of the team; entries from invoices and expenses show them a read-only summary. Someone who keeps several sets of books chooses between them under Books. Accountant access is on paid plans.
Accounting preview: accountant access
Teams on a paid plan can give an accountant access to their books without making them a team member.