Change the credit card shared by a Family Sharing group on Mac
As the family organizer, you can change the credit card shared by all family members.
For information about managing Family Sharing settings using an iOS or iPadOS device, see the Apple Support article Set up Family Sharing.
On your Mac, choose Apple menu > System Preferences, click Family Sharing, then select Purchase Sharing in the sidebar.
For Shared Payment Method, click Edit, then change the credit card information and billing address for your payment method.