You can give an accountant access to Gigwell, but invoice access is all-or-nothing — it can't be narrowed to one artist, or to only artist-fee or only booking-fee invoices. If you need a genuinely narrow view, a saved report is the better tool.
Give them an account
Go to Settings → Team/Users.
Add the accountant as a contact/user on your account.
Ask your accountant to log out and back in. Access doesn't take effect until they start a fresh session, which is the step that catches people out.
Have your accountant confirm they can reach what they need.
Or give them a report instead
If you'd rather they only saw invoices and nothing else:
Go to Reports.
Switch to the Invoices report tab.
Click Filters in the top right and set them to exactly the artist, date range or invoice type you want the accountant to see.
Click Create Report, and tick the option to include the invoice documents if they need the PDFs too.
Save the report so you can rerun it, and share the output with them each period.
This keeps their view scoped to exactly what you've filtered for, which a user account can't do.
Good to know
Invoice visibility can't be restricted by invoice type per user. A user who can see invoices sees all of them on the bookings they can reach.
Roles change what someone can do, not which invoices they can see. The Assistant role, for instance, can't create invoices but isn't a way to limit visibility.
If the accountant only ever needs figures at period end, the report route usually causes less friction on both sides than managing another user.