Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
To upgrade from Microsoft 365 Personal to Family, purchase the Family plan using the same Microsoft account you currently use on your Mac. Your remaining time on the Personal plan will automatically be converted to the Family plan.
First, sign in to the Microsoft Account Services page (https://account.microsoft.com/services) with your current Microsoft account. Find your Microsoft 365 Personal subscription and select Upgrade, or purchase Microsoft 365 Family directly while you are signed in. After you complete the purchase, your remaining days on the Personal plan will automatically convert and be added to your new Family subscription. You can continue using the Microsoft 365 apps on your Mac, so you do not need to reinstall them.
After upgrading, you can share the Microsoft 365 Family subscription with someone using a Windows 11 PC. Go to your Microsoft Sharing page (https://account.microsoft.com/services/office/sharing) and select Start sharing. Send the invitation link by email to the person using the Windows 11 computer. They can open the invitation, accept it, and sign in with their own Microsoft account. They can then install and use the Microsoft 365 apps on their Windows 11 PC.
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hth
Marcin