https://support.microsoft.com/en-us/office/get-help-with-product-key-errors-on-office-com-setup-e5064f7b-2a8d-4e77-bd59-f1d828086851#bkmk_acctlimits
The redemption process on https://office.com/setup and https://microsoft365.com/setup associates your Office product with your Microsoft account. Here are some important limits regarding your Microsoft account.
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Your Microsoft account can have only one Microsoft 365 Family subscription associated with it. If you use the same Microsoft account to buy or redeem multiple Microsoft 365 subscriptions, you extend the amount of time for your subscription, up to a maximum of 5 years. This doesn't increase the number of Office devices you can be signed in to or increase the amount of online storage that's available with the subscription. For more information, see What happens if I add another Office 365 for home subscription plan to my account? and How sign in works in Office 365.
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If you have Microsoft 365 Family and you need to support more than 6 people on your subscription, we recommend purchasing an Office 365 business subscription or volume license products of Office instead.
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You can redeem up to 25 one-time purchases of Office 2019, Office 2016, or Office 2013 on the same Microsoft account. If you'd like to purchase more than 25 copies of Office for work, we recommend purchasing an Office 365 business subscription or volume license products of Office instead.
