What Is the Census and How Does It Work?

The U.S. census is a count of every person living in the country, taken once every ten years as required by Article I, Section 2 of the Constitution.¹ It works by asking every household a short set of questions about who was living there on April 1 of the census year. The results decide how many seats each state gets in the U.S. House of Representatives and steer trillions of dollars in federal spending for the decade that follows. Everyone in the country is counted regardless of citizenship status, and federal law makes participation mandatory.

What the Count Decides

The most direct effect of the census is congressional apportionment: the 435 seats in the House of Representatives are divided among the 50 states based on each state’s share of the total population.² A state that grows relative to others can gain a seat; a state that lags can lose one. States then use the detailed census numbers to redraw their congressional and legislative districts, and federal law requires the Census Bureau to deliver that data by April 1 of the year after the count.

Race and ethnicity data from the census also underpins enforcement of the Voting Rights Act, since courts rely on those figures to judge whether districts dilute minority voting power.

Then there is the money. At least 353 federal assistance programs use census data to distribute funds, and in fiscal year 2021 those programs sent out more than $2.8 trillion for healthcare, highways, school lunches, housing assistance, and similar services.³ A community that is undercounted receives less than its share, and that shortfall lasts the full ten years until the next count corrects it.

Who Gets Counted, and Where

The census counts every person at the place where they live and sleep most of the time. April 1 is the reference date: you report your household as it stood that day.⁴ If you split time between two homes and genuinely cannot say which one you use more, you’re counted wherever you are staying on April 1.⁵

A few common situations cause confusion:

College students living away from home are counted at their campus or off-campus address, even if they happen to be visiting their parents on April 1. Students who commute from a parent’s home are counted there. Double-counting often happens when parents list a student who also gets counted at school.⁵
Service members stationed in the U.S. are counted where they live. Those deployed or stationed overseas are counted in their home state for apportionment. Their families living stateside are counted at their U.S. address.
People in group settings such as nursing homes, prisons, dorms, homeless shelters, and military barracks are counted at those facilities, which the Bureau contacts directly.⁶
Private U.S. citizens living abroad are generally not included; federal civilian employees and military members stationed overseas are counted for apportionment purposes.

What the Form Asks

The census questionnaire is short. The 2020 version asked fewer than a dozen questions per person.⁷ You’ll be asked:

How many people were living or staying in the home on April 1, including babies, relatives, roommates, and anyone without a permanent address elsewhere.
Whether the home is owned with a mortgage, owned outright, rented, or occupied without paying rent.
Each person’s name, sex, age, and date of birth. Babies under one year old are listed as age zero.
Each person’s Hispanic origin and race, asked as two separate questions with write-in space for specific origins or tribal affiliations.
How each additional person is related to the first person on the form.

The form does not ask about citizenship, immigration status, Social Security numbers, income, or bank or credit card information.⁷ Anyone asking you for that information in the name of the census is not doing legitimate census work.

One point of confusion worth clearing up: the decennial census is not the same as the American Community Survey. The ACS goes to a sample of households every year and asks much more detailed questions about income, education, commute times, disability, and health insurance.⁸ Response to the ACS is also required by law, but it is a separate program from the ten-year count.

How to Respond

The Census Bureau mails an invitation letter to every household with a 12-digit ID code.⁹ You can respond in three ways:

Online, by entering the ID code on the Census Bureau’s portal. Save the confirmation number you receive as proof of completion.
By mail, using the paper form and prepaid envelope sent with the invitation.
By phone, with a trained representative. For the 2020 count, the Bureau provided language guides in 59 non-English languages.¹⁰

Responding through any of these channels takes your household off the follow-up list. If you don’t respond, an enumerator will visit your address in person, typically between 9 a.m. and 9 p.m., to conduct the interview.¹¹ If repeated visits don’t reach anyone, the enumerator may ask a neighbor or building manager for basic information about the unit, such as whether it is occupied and how many people live there.

Is Participation Mandatory?

Yes. Federal law requires the Secretary of Commerce to conduct the decennial count, and a separate statute makes your response mandatory.¹² Under 13 U.S.C. § 221, anyone 18 or older who refuses or willfully neglects to answer can be fined up to $100. Intentionally giving false answers carries a fine of up to $500.¹³

In practice, the Bureau has not prosecuted individuals for non-response in decades and leans on outreach and follow-up visits instead. The legal authority remains on the books. The same statute explicitly says no one can be compelled to disclose their religious beliefs or affiliations.¹³

How Your Answers Are Protected

Census confidentiality is among the strongest privacy protections in federal law. Under 13 U.S.C. § 9, Bureau employees cannot use your individual responses for anything other than producing statistics. They cannot publish data in a form that identifies you, and no other agency, including the IRS, immigration authorities, and law enforcement, can access your individual responses.¹⁴ Census reports kept by individuals or households are immune from legal process and cannot be used as evidence in court or in administrative proceedings.

Bureau employees take a lifetime oath to keep the data confidential. Violators face up to five years in federal prison.¹⁵ The census statute caps the fine at $5,000, but the general federal sentencing statute raises the maximum to $250,000 for any felony, which unauthorized disclosure of census data qualifies as.¹⁶

Individual census records stay sealed from public view for 72 years after collection. During that time only the person named on the record or their legal heir can request access. Once the 72-year window closes, the National Archives makes the records public, which is why the 1950 census records became available in 2022.¹⁷

Spotting a Real Census Worker

If someone knocks on your door claiming to represent the Census Bureau, they must carry a government-issued photo ID badge showing their name, photograph, a Department of Commerce watermark, and an expiration date. They should also carry an official bag and a Census Bureau-branded electronic device such as a laptop or smartphone.¹¹ Legitimate enumerators visit between 9 a.m. and 9 p.m. local time.

A real census worker will never ask for your Social Security number, bank or credit card information, money or donations, or your mother’s maiden name.¹⁸ If anything feels wrong, call your regional Census Bureau office or the Customer Service Center to verify the visit before giving any information.

The Next Census

The next decennial count is scheduled for April 1, 2030. The Bureau ran a major field test on April 1, 2026, and has a second test planned for April 1, 2028, as a dress rehearsal for the actual count.¹⁹ The 2030 form is likely to look somewhat different: the Office of Management and Budget updated its race and ethnicity standards in 2024, and the Bureau is working toward a combined race-and-ethnicity question with seven co-equal categories, including a new “Middle Eastern or North African” option.²⁰ Whether a citizenship question appears on the 2030 form is unresolved. The prior attempt to add one to the 2020 census was blocked by the Supreme Court, and new legislative and legal efforts are underway.

1
Congress.gov. U.S. Constitution Article I – Section 2
2
U.S. Census Bureau. Congressional Apportionment
3
U.S. Census Bureau. Census Bureau Data Guide More Than $2.8 Trillion in Federal Funding in Fiscal Year 2021
4
U.S. Census Bureau. Census Day Is Here – Make It Count
5
U.S. Census Bureau. Residence Criteria and Residence Situations for the 2020 Census
6
U.S. Census Bureau. 2020 Census Group Quarters
7
U.S. Census Bureau. 2020 Census Informational Questionnaire
8
U.S. Census Bureau. American Community Survey
9
U.S. Census Bureau. Census Household Survey
10
United States Census Bureau. 2020 Census – Language Resources
11
U.S. Census Bureau. Verify a Census Bureau Survey, Mailing, or Contact
12
Office of the Law Revision Counsel. 13 USC 141 – Population and Other Census Information
13
Office of the Law Revision Counsel. 13 USC 221 – Refusal or Neglect to Answer Questions; False Answers
14
Office of the Law Revision Counsel. 13 USC 9 – Information as Confidential; Exception
15
Office of the Law Revision Counsel. 13 USC 214 – Wrongful Disclosure of Information
16
Office of the Law Revision Counsel. 18 USC 3571 – Sentence of Fine
17
U.S. Census Bureau. The 72-Year Rule
18
United States Census Bureau. Top Questions About the Survey
19
U.S. Census Bureau. Census Bureau Announces Updates for 2030 Census Planning
20
U.S. Census Bureau. Updates to Race/Ethnicity Standards for Our Nation