If the birthdate on a Microsoft account says that it belongs to a child, there are different steps to take in regions such as the United States of America and the Republic of Korea, and other regions that regulate what children can do online.
To change your own account from a child account to a full account, you need to prove that you're an adult. You have two options:
Microsoft Account Child Age Verification
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Redmond, WA 98052
Article ID: 12411 - Last Review: Apr 28, 2016 - Revision: 21