The most likely cause is that there are two separate Microsoft 365 Family subscriptions or two Microsoft accounts using the same payment method. Microsoft also notes that charges can appear close together when a previously declined payment is retried, but in this case the repeated yearly pattern points more strongly to duplicate subscriptions or different accounts.
Because the accounts appear linked, another possibility is that the same email address is being used as both a personal Microsoft account and a work or school account, which can cause sign-in confusion and make it seem like one account opens another.
Use this check path:
- Go to Services & subscriptions and sign in with the btinternet.com account.
- Check whether a Microsoft 365 Family subscription is active there, and note the renewal date.
- Sign out fully.
- Go back to Services & subscriptions and sign in with the outlook.com account.
- Check whether a second Microsoft 365 Family subscription is active there.
- Review order history for both accounts and look for charges of the same amount close together.
- If only one account shows the charge, go to Payment options / Manage your payments and select Investigate to check whether another Microsoft account is using the same card.
If both accounts show active subscriptions, that explains the double billing. One subscription can then be cancelled from the account where it is active. If a payment was taken after cancellation, Microsoft says this can happen when cancellation was made too close to the billing date, specifically less than 2 days before billing.
For the sign-in confusion between the two identities, if the prompt says “Which account do you want to use?”, Microsoft says that usually means there are two accounts with Microsoft using the same email address: a personal account and a work or school account. In that case, renaming the personal Microsoft account alias can help stop the prompt.
If the duplicate charge is confirmed and it is not clear which account owns it, use Investigate on the Manage your payments page or contact Microsoft Support through Contact Support for billing help.
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