You may have to pay taxes on your AdSense earnings. The exact regulations vary by contracting entity. Find out how to find your contracting entity. Note that it's your responsibility to understand and adhere to the appropriate tax rules; 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're required to provide tax information, details will be available on the "Payments > Settings" page in your AdSense account.
For specific information regarding US 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.