A group subscription allows you to purchase in bulk for any group, organization, or company. You will be able to modify group membership at any time. At this time, group subscriptions are only available for annual plans.
Navigate to https://subdomain.substack.com/subscribe?group=true (replace "subdomain" with the name of the publication).
An administrator can sign up, add the email addresses for the subscribers in the group, and pay with a single credit card.
Learn more on how to add members to your group subscription.