How Background Checks for Guns Work: Form 4473, NICS, and Denials

When you buy a firearm from a licensed dealer, the dealer runs your information through the FBI’s National Instant Criminal Background Check System, or NICS, before finalizing the sale. That is the core of how gun background checks work: you fill out ATF Form 4473, the dealer submits your identifying details to NICS, and the system searches three federal databases and returns one of three answers — proceed, delayed, or denied. Most checks clear in minutes. Some take days. A small share end the sale on the spot.

When a Background Check Is Required

Federal law requires the check whenever a Federal Firearms License holder transfers a firearm to an unlicensed buyer. The rule comes from 18 U.S.C. § 922(t), the permanent provision of the Brady Handgun Violence Prevention Act, and it covers retail stores, gun shows, and any other setting where a licensed dealer is the seller.¹

Federal law does not require a check for a private sale between two unlicensed individuals, though it remains illegal for anyone to sell a firearm to someone they know or have reason to believe is prohibited.² Roughly 22 states and Washington, D.C. have closed that gap for at least some private transfers, and about 19 states require checks for all firearm transfers regardless of who is selling.

Not every state routes the check the same way. In some, the dealer contacts the FBI directly. In others, the dealer contacts a state point-of-contact agency that runs its own databases alongside NICS. Either way, the buyer’s experience is broadly similar, though processing times and fees can differ.³

Filling Out Form 4473

The process begins with ATF Form 4473, the Firearms Transaction Record. You complete it at the dealer’s place of business before any check is initiated. Bring a valid government-issued photo ID showing your current address — typically a driver’s license or state ID card.⁴

The form asks for your full legal name, date of birth, place of birth, current address, and citizenship status. Providing your Social Security number is optional, but the FBI recommends it because it helps separate you from other people with similar names and reduces the chance of a false delay.

You then answer a series of yes-or-no questions about your legal history covering the federally prohibited categories. Signing certifies under penalty of perjury that every answer is truthful. Lying on Form 4473 is a federal felony punishable by up to five years in prison and a fine of up to $250,000.⁵

What NICS Checks

Once the form is done, the dealer submits your information to NICS through a secure electronic portal or by calling an FBI examiner. The system searches three federal databases at once:⁶

The Interstate Identification Index (III), a repository of criminal history records and felony convictions shared across jurisdictions.
The National Crime Information Center (NCIC), which holds records on active warrants, protective orders, fugitives, and other criminal justice data.
The NICS Indices, records submitted by federal, state, and local agencies specifically flagging people prohibited from buying firearms, including mental health adjudications and immigration-related disqualifiers.⁴

A clean record often clears the automated system almost instantly. Complications begin when a record in one of those databases returns a potential match that a human examiner has to review.

Proceed, Delayed, or Denied

The FBI returns one of three responses to the dealer:

Proceed. No disqualifying records were found and the sale can go forward.
Delayed. A potential match needs further investigation. An examiner reviews additional records to determine whether the match is actually you.
Denied. A confirmed disqualifying record exists, and the dealer cannot complete the sale.⁶

A delay is not a denial. It usually reflects a name, date of birth, or other detail that resembles someone in one of the databases. Many delayed checks resolve to “proceed” after manual review.

The Three-Business-Day Default Transfer

If a check stays in “delayed” status and the FBI has not issued a final decision after three business days, the dealer may legally transfer the firearm. The clock starts the day after the check is initiated and does not count weekends or federal holidays.⁶ Dealers are not required to release the firearm at three days; some wait longer as a matter of policy, and some states prohibit any transfer until the check fully resolves. Several states also impose their own waiting periods on top of the NICS process, so an instant clearance does not always mean same-day pickup.

Extra Steps for Buyers Under 21

The Bipartisan Safer Communities Act of 2022 added scrutiny for buyers between 18 and 20 years old. When the check involves someone under 21, NICS examiners must contact additional agencies beyond the three standard databases:⁷

State juvenile justice agencies
State mental health agencies
Local law enforcement where the buyer lives

Those agencies have three business days to respond. If potentially disqualifying juvenile information surfaces in that window, the FBI can extend the investigation up to a total of 10 business days, and the standard three-day default transfer does not apply during the extension.⁸

Who Cannot Pass a Check

Under 18 U.S.C. § 922(g), federal law prohibits several categories of people from possessing firearms or ammunition:⁹

Anyone convicted of a crime punishable by more than one year in prison, regardless of the actual sentence served.
Fugitives from justice, meaning anyone with an active warrant or who has fled a jurisdiction to avoid prosecution.
Anyone who currently uses or is addicted to a controlled substance, including marijuana under federal law.
Anyone formally adjudicated as mentally incompetent or involuntarily committed to a mental institution.
Certain noncitizens, including anyone unlawfully present in the United States or admitted on a nonimmigrant visa, with limited exceptions.
Anyone dishonorably discharged from the U.S. Armed Forces.
Anyone who has renounced U.S. citizenship.
Anyone subject to a qualifying protective order issued after a noticed hearing that restrains them from threatening or harassing an intimate partner or child.
Anyone convicted of a misdemeanor involving the use of physical force against a spouse, former spouse, co-parent, or cohabiting partner.
Anyone currently under indictment for a crime punishable by more than one year in prison.

The drug-use category catches many buyers off guard. Marijuana remains a Schedule I controlled substance under federal law, so a user is a prohibited person even in a state that has legalized recreational or medical use. Form 4473 states explicitly: “The use or possession of marijuana remains unlawful under Federal law regardless of whether it has been legalized or decriminalized for medicinal or recreational purposes in the state where you reside.”¹⁰ Answering that question dishonestly is a federal felony, and holding a state-issued medical marijuana card gives the dealer reasonable cause to believe you are prohibited.

If You Are Denied or Repeatedly Delayed

If NICS denies the sale, you have the right to learn why and to challenge the decision.¹¹ The dealer should give you a NICS Resolution Card with the NICS Transaction Number tied to your denial. You will need that number to file an appeal.¹²

Appeals go to whichever agency ran the check. Where the FBI ran it directly, you submit the appeal to the FBI’s NICS Section. In point-of-contact states, you start with the state agency, though you can also submit the appeal to the FBI Criminal Justice Information Services Division. Include your full name, mailing address, and the transaction number.

Supporting documents matter. Certified court records showing a conviction was expunged, a restraining order was lifted, or charges were dismissed can resolve the issue. Fingerprint cards help when the problem is a name match with someone else’s criminal record.

If you are repeatedly delayed or mistakenly denied because your identifiers resemble those of a prohibited person, you can apply for the FBI’s Voluntary Appeal File. The program places your details on file so future NICS checks can more quickly confirm you are not the flagged individual.¹³ Enrollment does not guarantee instant approval; a full check still runs each time. But it materially reduces the odds of a false hit pulling you into another multi-day delay.

Straw Purchases Are a Separate Crime

Buying a firearm on behalf of someone who cannot pass a check is a federal crime known as a straw purchase. The Bipartisan Safer Communities Act created a standalone statute at 18 U.S.C. § 932, carrying up to 15 years in prison, and up to 25 years if the firearm is intended for use in a felony, an act of terrorism, or drug trafficking.¹⁴

Form 4473 asks directly whether you are the actual buyer. Answering “yes” while really purchasing for someone else is both a false statement on the form and a straw purchase, and federal prosecutors treat these cases seriously. A legitimate gift is the common exception: you can buy a firearm as a present for someone legally eligible to own one, because at the moment of purchase you are the true buyer.

1
Bureau of Alcohol, Tobacco, Firearms and Explosives. Brady Permit Chart
2
Office of the Law Revision Counsel. 18 USC 922 Unlawful Acts
3
Federal Bureau of Investigation. NICS Participation Map
4
Federal Bureau of Investigation. Firearms Checks (NICS)
5
Office of the Law Revision Counsel. 18 US Code 924 – Penalties
6
Federal Bureau of Investigation. About NICS – Section: How Firearms Background Checks Work
7
Federal Bureau of Investigation. NICS Enhanced Background Checks for Under-21 Gun Buyers Showing Results
8
Federal Bureau of Investigation. Crime Data – Bipartisan Safer Communities Act
9
Office of the Law Revision Counsel. 18 US Code 922 – Unlawful Acts
10
Bureau of Alcohol, Tobacco, Firearms and Explosives. Firearms Transaction Record – ATF Form 4473
11
Federal Bureau of Investigation. Requesting Reason for and/or Challenging a NICS-Related Denial
12
Federal Bureau of Investigation. NICS Guide for Appealing
13
Federal Bureau of Investigation. Voluntary Appeal File Application Form
14
Office of the Law Revision Counsel. 18 USC 932 Straw Purchasing of Firearms