A Gun Bill of Sale (also called a Firearm Bill of Sale) is a legal document that records the private transfer of a firearm from the seller to the buyer. Firearm sales in the United States are regulated at both the federal and state levels, with significant variation in requirements depending on the jurisdiction. At the federal level, the Gun Control Act of 1968 (GCA, 18 U.S.C. Chapter 44) and the Brady Handgun Violence Prevention Act of 1993 (18 U.S.C. Section 922(t)) establish the framework for firearm sales, including prohibited person categories, licensed dealer requirements, and background check procedures.

Under federal law, private sales between residents of the same state (sometimes called the "private sale exemption" or "gun show loophole") are not required to go through a Federal Firearms Licensee (FFL) or undergo a National Instant Criminal Background Check System (NICS) background check, unless state law imposes additional requirements. However, it remains a federal felony under 18 U.S.C. Section 922(d) to sell or transfer a firearm to any person the seller knows or has reasonable cause to believe is a prohibited person (felons, domestic violence misdemeanants, persons under indictment, illegal drug users, adjudicated mental defectives, and others listed in 18 U.S.C. Section 922(g)).

State laws on private firearm sales vary dramatically. States such as California, Colorado, Connecticut, Delaware, New York, Oregon, Washington, and others require universal background checks for all firearm transfers, including private sales, which must be conducted through an FFL. Other states have no additional requirements beyond federal law for private sales. Some states require a permit to purchase or a firearm owner identification card. The bill of sale, while not federally mandated, creates a critical record that protects both the seller and buyer by documenting that the transfer occurred, the identities of the parties, and the date ownership changed hands.

A private individual is selling a firearm to another private individual within the same state and needs a written record of the transfer documenting the seller's divestment of the weapon and the buyer's assumption of ownership and responsibility. A gun owner is purchasing a firearm from a private seller and wants documentation proving they acquired the weapon legally, which may be needed if the firearm is later used in a crime or traced by law enforcement.

A person is selling a firearm collection or individual firearms from a deceased family member's estate and needs documentation for each sale for probate accounting and to establish the chain of custody. A firearm owner is gifting a gun to a family member and needs to document the transfer, which may require an FFL transfer and background check in universal background check states.

A gun owner is transferring a firearm to an FFL dealer for consignment sale, trade-in, or gunsmith services and needs documentation of the transfer. A person is moving to a new state and needs to document their existing firearm ownership, as some states require registration or notification for firearms brought into the state.

A buyer or seller wants protection against future liability. The seller's copy of the bill of sale demonstrates they no longer possessed the firearm after the date of sale, which is relevant if the firearm is later used in a crime or found at a crime scene.

The seller's and buyer's full legal names, addresses, dates of birth, and government-issued identification numbers (driver's license or state ID) must be documented. Both parties should verify the other's identity by examining a valid government-issued photo ID. The buyer should confirm they are a resident of the same state as the seller (interstate private sales without an FFL are prohibited under 18 U.S.C. Section 922(a)(5)).

The firearm description must include the make (manufacturer), model, caliber or gauge, serial number, type (handgun, rifle, shotgun), barrel length, and finish. The serial number is the most critical identifier and must be verified against the physical firearm. The seller should verify the firearm is not reported stolen by checking with local law enforcement or using available databases.

A legal compliance section should include representations from both parties. The seller should represent that they are the lawful owner, that the firearm is not stolen, and that they have no knowledge that the buyer is a prohibited person. The buyer should represent that they are not a prohibited person under 18 U.S.C. Section 922(g), that they are legally eligible to possess firearms under federal and state law, that they are a resident of the state where the transaction occurs, and that they are of legal age (18 for long guns, 21 for handguns under federal law).

The purchase price and payment method must be documented. The date, time, and location of the sale should be recorded. The bill of sale should note whether the transaction was conducted through an FFL and whether a background check was performed, as required by some state laws.

Both parties must sign and date the document. Each party should retain a copy indefinitely. Some practitioners recommend having the bill of sale notarized, though this is not legally required. The seller should include a statement that they have no further responsibility for the firearm after the date of transfer. In universal background check states, the bill of sale should reference the FFL's name, address, and license number where the transfer was processed.