You may have to pay taxes on your AdMob earnings. The exact regulations vary by contracting entity. It is your responsibility to understand and adhere to the appropriate tax rules, and Google is unable to provide you with tax advice.
Google is required by United States tax laws to collect certain tax-related information from some publishers. If you are required to provide tax information, go to Payments > Manage settings and the option will be available in the "Payments profile" section.
For specific information regarding U.S. tax requirements, please visit the IRS website.
Any tax-related information provided by Google is not intended as and should not be construed as legal, tax, or investment advice. For tax advice or more technical questions about how tax laws apply to you, please consult your tax advisor.