A Microsoft file hosting and synchronization service.
Turn off recurring billing on your wife’s existing subscription, allow it to run until the paid end date, and then have her accept your Microsoft Family invitation. Her OneDrive files and cloud data remain safe throughout the transition because they stay associated with her existing Microsoft account.
First, turn off auto-renewal. Your wife should sign in to her Microsoft Services page, select Manage next to her subscription, and choose Turn off recurring billing (or cancel in a way that allows the subscription to expire at the end of the paid period). This prevents future charges while allowing her to continue using all subscription benefits until the expiration date.
Her files do not need to be moved or copied. Her personal OneDrive account and stored files remain intact under her existing Microsoft login. She will continue accessing the same account and data; the subscription change does not delete or transfer anything.
After the subscription expires, she can join your Microsoft Family plan. Microsoft generally does not allow an account with an active standalone Microsoft 365 subscription to switch directly to a shared Family subscription, so she must wait until the current paid subscription officially ends and the account status changes to expired.
Once the subscription has expired, go to your Microsoft Family dashboard, select the option to share Microsoft 365, and send her an invitation. She should accept the invitation (typically within the stated invitation validity period) using the same Microsoft account. After acceptance, her account will receive the Microsoft 365 Family benefits, including the shared 1 TB OneDrive storage allocation.
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hth
Marcin