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Component ID: #ti292414743

Boundary and Annexation Survey (BAS) Overview

The U.S. Census Bureau conducts the Boundary and Annexation Survey (BAS) annually to collect information about selected legally defined geographic areas. The BAS is used to update information about the legal boundaries and names of all governmental units in the United States. The Census Bureau uses the boundary information collected in the BAS to tabulate data for the decennial and economic censuses, and annual estimates and surveys such as American Community Survey (ACS) and the Population Estimates Program (PEP).

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Why Participate?

  • Boundary updates complete the Census Bureau’s geographic framework for data collection, tabulation, and dissemination, and are vital to the success of the 2020 Census, the American Community Survey (ACS), Population Estimates Program (PEP), and many other censuses and surveys.
  • The federal government allocates more than $675 billion in federal funds annually for health, welfare, infrastructure, education, and other federal programs and services. Responding to the BAS ensures that your local government receives the funds for which it is entitled and has the best data available for its decision-making processes.

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How To Participate?

Step 1A:  Review your boundary using one of the following options:

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For more information on TIGERweb, please see:

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Step 1B:  Review legal boundary change and annexation data:

  • Review the legal boundary change and annexation data to confirm that the Census Bureau correctly recorded legal documentation from last year's BAS.

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Step 2:  Complete the Annual Response Form to:

  • Review and update contact information.
  • Report ‘No Changes’ if you have no boundary changes to submit.
  • Select a response method if you have boundary changes to submit.

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Step 3:  Submit boundary changes:

  • For Digital BAS or GUPS Users - Use the Secure Web Incoming Module (SWIM) to securely transfer your updates to the Census Bureau. If you require assistance with the SWIM, contact the Census Bureau via email at or via telephone at 1-800-972-5651.

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  • For Paper BAS Users - Use the provided pre-paid envelope to return BAS paper maps to the Census Bureau.

Related Information

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