BAS-Local

The Boundary and Annexation Survey (BAS) is an annual Census Bureau program that gives eligible tribal, state, and general-purpose local governments the opportunity to review the Census Bureau's legal boundary data and confirm that the agency has the correct boundary, name, and status information for their jurisdiction. Maintaining accurate boundaries matters directly for local governments because the Census Bureau uses the boundaries collected through BAS to tabulate data for the decennial census, the American Community Survey, and the Population Estimates Program. BAS is a voluntary program with an annual March 1 submission deadline; local governments can participate using the Census Bureau's free Geographic Update Partnership Software (GUPS) or the BAS Partnership Toolbox for ArcGIS Pro.

U.S. Census Programs for Local Governments

Census Block Boundary Suggestion Project (BBSP)

U.S. Census Bureau Voting District Project (VTDP)

Census Local Update
of Census Addresses
Operation (LUCA)

BAS Updates and Info

The Boundary Annexation Survey (BAS) Submission Checklist for Local Governments

July 14, 2026

DATA and TECHNOLOGY Local Redistricting

The Boundary Annexation Survey (BAS) Submission Checklist for Local Governments

The Boundary and Annexation Survey (BAS) is the Census Bureau's annual check-in with local government ...

BBSP vs. BAS: Two Census Programs, Two Crucial Jobs

June 4, 2026

DATA and TECHNOLOGY Local Redistricting

BBSP vs. BAS: Two Census Programs, Two Crucial Jobs

The Boundary and Annexation Survey (BAS) and the Block Boundary Suggestion Project (BBSP) are often ...

Why the Boundary and Annexation Survey (BAS) Matters for Local Redistricting Officials

December 15, 2025

Census Data and Geography Local Redistricting

Why the Boundary and Annexation Survey (BAS) Matters for Local Redistricting Officials

Every year, the U.S. Census Bureau invites tribal, state, and general-purpose local governments, counties, cities, ...

Video Resources

2026 Boundary and Annexation Survey (BAS) Webinar

Mar 5 2026: TThe Boundary and Annexation Survey (BAS) is an annual opportunity for tribal, state, and general-purpose local governments to review and update the U.S. Census Bureau's legal boundary data. This webinar will provide a high-level overview of BAS, demonstrate how to complete a BAS submission using the BAS Partnership Toolbox for ArcGIS Pro, demonstrate how to complete a BAS submission using the Geographic Update Partnership Software (GUPS) Web application, and how to return BAS updates using the Secure Web Incoming Module (SWIM).

GUPS Web for BAS - Introduction

Apr 2025 : This video will provide a high-level overview of the U.S. Census Bureau's online Geographic Update Partnership Software (GUPS) Web for the Boundary and Annexation Survey (BAS)

2021 Boundary and Annexation Survey (BAS) Webinar - Overview

Jan 2021: This video provides a high-level overview of BAS, explains the purpose of the program, provides participation information, and lists the benefits of taking part in the program.

2021 Boundary and Annexation Survey (BAS) Webinar - How to Participate

Jan 2021: This video introduces the BAS Annual Response email, and explains the importance of reviewing the Census Bureau’s boundary data before determining whether there are boundary changes to report to BAS,

2021 Boundary and Annexation Survey (BAS) Webinar - BAS Agreements

Jan 2021: This video provides information on the various BAS agreements the Census Bureau maintains with state and local governments. A demonstration will follow of how to find which governments participate in one of these agreements and how to create or join an existing agreement.

2021 Boundary and Annexation Survey (BAS) Webinar - BAS State Certification Program

Jan 2021: This video provides information on the BAS State Certification Program, which is a BAS-related program that provides an annual opportunity for state agencies to verify updates reported through BAS are in accordance with state law.

Introduction to the Tribal Boundary and Annexation Survey (BAS)

Jan 2021: Tribal BAS is an annual opportunity for Tribal governments to review and update the legal boundary data the U.S. Census Bureau has on file. This video introduces Tribal geography, an overview of Tribal BAS, and additional resources for Tribal BAS participants.

2026 Boundary and Annexation Survey (BAS) Webinar

BAS Resources & Guides

Program Overview

Choosing a Response Method

The Bureau lists three response methods for preparing a BAS submission: the Partnership Toolbox, GUPS Web, and paper.

Partnership Toolbox Pro runs inside ArcGIS Pro 3.0 or higher (not ArcGIS Desktop), so it requires a licensed Esri installation and GIS staff. It automates data download, change creation, sliver removal, attribution formatting and checks, and export.
GUPS Web is a customized web-based GIS application — no desktop GIS required. It imports local boundary data, automates change creation, allows manual edits, and exports standardized submission files. If a government wants to use it for the 2026 BAS, it indicates that on the Annual Response Form.
Paper BAS is designed for participants who prefer to update their boundary on paper maps. Participants annotate their boundary, feature, and attribute changes on Census Bureau-provided paper maps using the instructions in the Paper BAS How-to Guide. To reduce cost, the Bureau asks participants to review their boundaries online before requesting the paper maps needed to complete the survey.

Information for Respondents: the four-step response sequence.
Response Methods: Partnership Toolbox, GUPS Web, and paper compared.
Respondent How-To Guides: index page for the guides below.

Preparing and Submitting

Reviewing Boundaries Before Submitting

Mapping Tools

Technical Documentation

Coordination, Guidance, and Legal Documents

2026 BAS Maps

The Boundary Annexation Survey (BAS) Submission Checklist for Local Governments

BBSP vs. BAS: Two Census Programs, Two Crucial Jobs

Why the Boundary and Annexation Survey (BAS) Matters for Local Redistricting Officials

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