The BAS ID is the number the Census Bureau uses to identify each government. BAS IDs can be found on the BAS Code Lists webpage.

The Boundary and Annexation Survey (BAS) is authorized by Section 6 of Title 13 of the United States Code. The Office of Management and Budget (OMB) approves the survey materials. The current valid OMB control number is OMB No. 0607-0151; approval expires on 11/30/2024. BAS is a voluntary survey.

The Census Bureau uses the boundaries collected in BAS to tabulate data for various censuses and surveys including the decennial census, American Community Survey, and Population Estimates Program. BAS fulfills the agency’s responsibility as part of the National Spatial Data Infrastructure, for which the Office of Management and Budget Circular A–16 designates the Census Bureau as the lead federal agency for maintaining national data about legal government boundaries, as well as statistical and administrative boundaries.

The BAS contact will receive an annual response email in early January. Governments that do not respond by late January, or those where we do not have an email address on file will receive an annual response letter by mail. We request all governments respond online to update contact information and to report if their government has legal boundary, name, or status updates to report.

Respond Now

The first BAS deadline is March 1. Boundary updates returned by this date will be reflected in the American Community Survey and Population Estimates Program data, and in next year’s BAS materials.

The final BAS deadline is May 31. Boundary updates returned by this date will be reflected in next year’s BAS materials.

For more information, see the BAS Schedule.

There are various ways to submit boundary changes through BAS. The Response Methods webpage provides further information.

You can include all of your legal changes in your submission. We will process them accordingly per the effective date provided. Legal changes that are effective after January 1 will not be processed for inclusion in the current year’s Census programs, such as the American Community Survey and Population Estimates Program. They will be processed at a later date and will be included in the following year’s BAS products.

If your government does not have any changes to report for this BAS cycle, you may complete the online annual response form, or notify the Census Bureau at geo.bas@census.gov. If you choose to notify the Census Bureau by email, please type "no boundary changes" in the subject heading and provide the following contact information for your Highest Elected Official and, if different, the BAS contact:

• Name
• Title
• Government Name
• Mailing Address
• Phone and Fax number
• Email Address

Respond Now

As a county respondent, we are asking you to review your county boundary and provide updates as needed. However, many county respondents also report changes for the legal governments (incorporated places and minor civil divisions) within their jurisdiction. Some counties have entered into a Consolidated BAS (CBAS) agreement with those governments, which states that the county will be responsible for reporting changes for all (or a portion of) governments within the county, reducing duplication of effort.

For more information, visit the BAS Agreements webpage.

Consolidated BAS (CBAS) agreements are agreements between a county and the governments in its jurisdiction, which provide an opportunity for county level governments to submit changes to BAS on behalf of some or all of the governments in their jurisdiction.

The CBAS program helps to reduce the burden on local governments and avoid duplication of efforts for governments participating in BAS. Once a local government joins a CBAS agreement, the local government will no longer receive BAS materials. Instead, the county BAS respondent will be responsible for providing the Census Bureau with all boundary updates. If you are interested in establishing a CBAS agreement, please email geo.bas@census.gov with your request.

For more information, visit the BAS Agreements webpage.

Yes. County participants can, but are not required to report boundary updates for governments within its jurisdiction.

If you are interested in reporting changes for place or minor civil division governments within your county, the Census Bureau offers consolidated BAS (CBAS) agreements. At the county level, a county government can provide updates for their county boundary, as well as for governments within the county that agree to the consolidation. Counties participating in a CBAS agreement are required to obtain the permission of the governments for which they will report. If your state has legislation in place requiring governments to report boundary changes to the county, then we ask only that you provide us this documentation. The Census Bureau will not mail the affected governments a BAS package next year or any subsequent year after a CBAS agreement has been completed.

For more information, visit the BAS Agreements webpage.

If you are a newly incorporated government, please notify the Census Bureau at geo.bas@census.gov. In order to process the new incorporation, the Census Bureau will need:

• A copy of the official new incorporation papers, including date of incorporation.
• A map indicating the boundaries of the new incorporation.
• Contact information for the Highest Elected Official and a contact for BAS.

Boundary updates received by March 1 that were effective by January 1 of the same year will be reflected in the American Community Survey and Population Estimates Program data and in next year’s BAS materials. Boundary updates received after March 1 but before May 31 will be reflected in next year's BAS materials.

For more information, see the BAS Schedule.

The goal of BAS is to update our geographic database according to the differences and/or changes between the Census-provided shapefiles and your local data. Those differences and changes should be reported as individual polygons that are coded according to the instructions found in the corresponding guide on the How-to Guides webpage. Individual change polygons allow us to process changes to our database in a uniform manner, while also providing us with the required information needed for legal changes and boundary corrections. Both the BAS Partnership Toolbox and GUPS Web allow users to import their own boundary shapefile and automatically create the changes.

The Census Bureau maintains files containing all previously submitted legal documentation through BAS on the Legal Boundary Change/Annexation Data webpage.

We recommend using the following Census-provided shapefiles regardless of the level of geography being reported for: edges, place, mcd/ccd, county, and water. If you are providing changes to Area Landmarks and/or Point Landmarks, those shapefiles should be used as well (arealm and pointlm). If you create your submission digitally using either the BAS Partnership Toolbox or the Geographic Update Partnership Software (GUPS), you will be given the option of having the shapefiles automatically downloaded and brought into your project.

The BAS contact is emailed a Secure Web Incoming Module (SWIM) token 5 days after submitting their annual response form.

If you downloaded shapefiles and did not notify us that you had changes to report, please fill out the online annual response form and the BAS contact will be sent a SWIM token in 5 days. In that time, please review your submission by referring to the documents on the How-to Guides webpage to ensure your submission is in the correct format.

Note: If a participant has an existing registered SWIM account they only need to login with their username and password. Both the username and password are case sensitive.

There are multiple accepted methods to create a Digital BAS submission using GIS. We recognize that users possess a wide range of experience and expertise in GIS, which allows a person to create a submission in many different ways. However, we do recommend using the BAS Partnership Tools in ArcGIS Desktop or ArcGIS Pro. Corresponding step-by-step instructions can be found on the How-to Guides webpage.

The BAS Partnership Toolbox will automatically rename your changes layer using the standardized naming conventions requested by the Census Bureau during the export process.

If you are not using the BAS Partnership Toolbox, the naming convention list for all shapefiles can be found in the BAS Technical Guide. The zip folder with shapefiles should be named ‘bas<yy>_<basID>_return’ (for example: bas24_10100012345_return).

The BAS Partnership Toolbox is now offered for both ArcGIS Desktop and ArcGIS Pro. Both versions of the Digital BAS Partnership Toolbox are available for download from the BAS Partnership Tools webpage.

You will need to add the toolbox to your ArcToolbox window or navigate to the toolbox in ArcCatalog.

To display the tools in ArcMap:

Open the ArcToolbox window. Right-click in the white space and click on Add Toolbox. Navigate to the location you saved the extracted DBAS folder and then into the setup folder. Click on Partnership BAS Tools toolbox and click Open. The toolbox should appear in your list of toolboxes.

To display the tools in ArcCatalog:

Open the Catalog Tree window in ArcCatalog. Navigate to the location you saved the extracted DBAS folder and then into the setup folder. The toolbox should appear there.

Download the BAS Partnership Toolbox

For help with the BAS Partnership Toolbox, please contact the Census Bureau at geo.bas@census.gov or call 1-800-972-5651.

The BAS Partnership Toolbox is available for ArcGIS Pro. These are two separate toolboxes, and they cannot be used interchangeably. For more information, see the BAS Partnership Tools webpage.

You need to enable the GUPS plugin.  At the top of the QGIS window there will be a Plugins menu item. Click Manage and Install Plugins>> and select the All tab on the left. Be sure gupsapp is checked. The GUPS BAS toolbar should then be displayed.

If the error you have keeps occurring please take a screenshot and send it to geo.bas@census.gov. We recommend that you close GUPS at the end of each business day to prevent the software from creating unwanted errors.

When you open GUPS the first time you will receive the error. Close the program. Open the program again and it should work normally. (Note: You may need to check the gupsapp program within the "Plugins" menu of QGIS to activate it.)

GUPS/QGIS uses Python. Other software that requires Python, most notably Esri products, may use other versions of Python causing GUPS/QGIS to fail to load. If this is an issue, please make sure to have the correct version of Python loaded onto your machine that GUPS was installed with.

Full step-by-step instructions on creating your Paper BAS submission can be found in the BAS Paper How-to Guide. Colored pencils are included in the original mailing package. We ask that you use the red pencil to update any changes to the boundary of your government and the purple pencil to make any changes to the road networks, address ranges, or areal features (parks, airports, etc.) within your government. Note that changes made in lead pencil or pen are sometimes more difficult to recognize due to existing symbology color.

You have a choice of returning your maps via US Postal Service with the Business Reply Label or via FedEx with the Pre-Paid Return Label included in your original mailing. Please only return maps that have changes on them. Please refer to the BAS Paper How-to Guide to ensure your submission is in the correct format.