Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
If you are being charged both $9.99 per month and $99 per year for Microsoft 365, you are probably paying for two separate Microsoft 365 subscriptions or services. A normal Microsoft 365 Personal subscription is generally billed either monthly or annually, not both, so seeing both charges usually means there are two subscriptions, two Microsoft accounts, or an additional subscription purchased through a different billing channel.
The $9.99/month charge could be a monthly Microsoft 365 subscription, while the $99/year charge could be an annual Microsoft 365 subscription on another account. It is also possible that one of the charges is for a different Microsoft service or was purchased through Apple, Google, Amazon, or another retailer, in which case it may not appear in the same Microsoft billing account.
To determine exactly what you are paying for, sign in at https://account.microsoft.com/services using each Microsoft account you have and check Services & subscriptions. Look for the subscription name, renewal date, billing frequency, and payment method. You should also check Order history at https://account.microsoft.com/billing/orders to identify the specific $9.99 and $99 charges.
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hth
Marcin