If your client is paying for their own subscription, they can invite you to that subscription so you can collaborate.

You will have full access to all your client’s live data from payroll or accounting.

You can share your Accountant ID with your client or select Copy link from your invitation section. You don't need to share both.

You'll need to send to your client an email with a quick explanation of what they need to do. You might want to send them a link to the help topic Invite an accountant.