To look up a county code, first decide which one you need. For a federal five-digit FIPS/ANSI code (used on census, disaster, and most federal forms), use the U.S. Census Bureau’s ANSI/FIPS code list or its address-based geocoder. For a state tax jurisdiction code (used on sales, use, and payroll tax filings), use your state department of revenue’s own lookup tool. The two systems produce different numbers for the same place, so the form you’re filling out determines which one to search.
Look Up a Federal FIPS or ANSI County Code
The Census Bureau’s ANSI/FIPS codes page is the authoritative source. It publishes downloadable files listing every county and county-equivalent entity in the country with its two-digit state code and three-digit county code.1U.S. Census Bureau. ANSI and FIPS Codes If you know the state and county name, the file is the fastest path: open it, find the row, copy the code.
If you only know a place name and want to search interactively, the Census Bureau directs users to the Geographic Names Information System (GNIS), maintained by the U.S. Board on Geographic Names. GNIS returns the associated federal codes along with other geographic identifiers.
If you have a street address and aren’t sure which county it falls in, use the Census Geocoder. Enter the address and the tool returns every geographic entity the point sits inside, including the county FIPS code.2U.S. Census Bureau. Census Geocoder This matters more than people expect, because municipal boundaries and county lines don’t always align, and a mailing city can sit in a different county than its name suggests.
One note on terminology. NIST withdrew the old FIPS 6-4 standard on September 2, 2008 and replaced it with INCITS 31-2009 under the ANSI umbrella.3National Institute of Standards and Technology. Replacement Standards for Withdrawn FIPS on Geographic Codes The numbers themselves barely changed, and most agencies still call them “FIPS codes.”1U.S. Census Bureau. ANSI and FIPS Codes If a form asks for a FIPS county code, the current Census file has the number you want.
Look Up a State Tax Jurisdiction Code
For anything tax-related, go straight to your state’s department of revenue website. Most offer an address-based lookup that returns the specific tax jurisdiction code and the current combined rate for that location. Enter the physical address of the business or the transaction, not a mailing address, because tax boundaries follow the physical location.
State codes vary widely in length and format. Some are three or four digits, some are alphanumeric, and they’re designed to distinguish overlapping taxing districts, such as an incorporated city with its own sales tax sitting inside a county that also collects one. The federal FIPS code for that county won’t tell the state anything useful about which district a sale belongs to.
If your state participates in the Streamlined Sales Tax program, standardized rate and boundary files are available through the Streamlined Sales Tax Governing Board and are updated quarterly.4Streamlined Sales Tax Governing Board. Rate and Boundary Files Non-participating states usually publish their own GIS-based lookup tools on a semiannual or quarterly schedule. Because district boundaries can change mid-year, pull the current file rather than reusing one you saved months ago.
What the Five-Digit Federal Code Actually Contains
Knowing the structure helps you spot mistakes. The full federal county identifier is five digits: two for the state, three for the county or equivalent within that state. In 48041, “48” is Texas and “041” is a specific county within Texas.1U.S. Census Bureau. ANSI and FIPS Codes The state prefix is what lets two counties in different states share the same three-digit number without collision.
The system covers more than counties in the strict sense. It includes Louisiana’s parishes, Alaska’s boroughs, Virginia’s independent cities, and the District of Columbia. Some forms want the full five-digit code, others just the three-digit county portion; check the field label before entering.
Common Pitfalls
Leading Zeros Disappear in Spreadsheets
This is the single most common error people make with county codes. A code like “041” or “007” loses its leading zero the moment a spreadsheet treats the column as a number, turning “041” into “41.” That either matches a different county or breaks any system expecting three digits. Format the column as text before you import or type anything. If the damage is already done, pad the values back to three digits, but catching it up front is far easier than reconciling mismatched records later.
Federal and State Codes Are Not Interchangeable
A three-digit federal FIPS code and a three-digit state revenue code for the same place will almost always be different numbers. Don’t copy one into a form that asks for the other. The form instructions or the agency’s website will say which system it uses.
Boundaries and Codes Change
County boundaries, names, and codes do change over time. The Census Bureau documents new entities, deletions, name changes, and code corrections through its geographic boundary change notes.5U.S. Census Bureau. Geographic Boundary Change Notes The most significant recent example: starting in 2024, the Census Bureau adopted Connecticut’s nine planning regions as county-equivalent units, replacing the state’s eight legacy counties in federal datasets. A pre-2024 Connecticut code no longer maps to the same geography. If your code list is more than a year or two old, verify it against the current Census file before you use it on anything official.