Massachusetts requires firearms to bear a qualifying serial number unless an applicable statutory or regulatory exemption applies.
Serialization and registration are separate legal requirements.
GOAL's current guidance identifies October 2, 2026 as the general serialization deadline for firearms subject to M.G.L. c. 140, §121C.
Does My Firearm Have to Be Serialized?
Massachusetts Firearm Serialization Navigator
Answer the questions below for a starting-point explanation of Massachusetts firearm serialization requirements.
1. What Is Serialization?
Massachusetts defines serialization as the process of permanently placing a unique serial number on the frame or receiver of a firearm.
Under M.G.L. c. 140, §121 and §121C, the serial number must be:
- conspicuously placed on the firearm frame or receiver;
- unique;
- placed so that it is not readily susceptible to being removed, altered, or obliterated;
- engraved, cast, or otherwise permanently embedded;
- at least .003 inches deep; and
- in a print size of at least 1/16 inch.
2. What Items Are Covered?
501 CMR 20.00 applies to firearms possessed, manufactured, or assembled in Massachusetts unless specifically exempted.
For purposes of these requirements, Massachusetts' definition of firearm includes certain:
- pistols;
- revolvers;
- rifles;
- shotguns;
- large-capacity firearms;
- assault-style firearms;
- machine guns;
- frames;
- receivers; and
- unfinished frames or receivers.
3. General Serialization Rule
M.G.L. c. 140, §121C states that firearms subject to the statute must have a qualifying serial number.
The statute also prohibits knowingly possessing, manufacturing, assembling, purchasing, offering for sale, selling, transferring, or importing an untraceable firearm in Massachusetts, subject to the exceptions and grace periods contained in the law.
4. What Is an Untraceable Firearm?
Massachusetts defines an untraceable firearm generally as:
- a firearm that has not been serialized; or
- a firearm whose serial or identification number has been removed, defaced, altered, obliterated, or mutilated.
5. October 2, 2026 Deadline
GOAL's current Chapter 135 guidance states that firearms subject to the new Massachusetts serialization requirement must have a qualifying serial number by October 2, 2026.
This deadline is separate from the Commonwealth's firearm registration requirements.
Registration answers: "Has this firearm been entered into the Massachusetts registration system?"
6. Privately Made Firearms
M.G.L. c. 140, §121C provides that a person may not manufacture or assemble a privately made firearm without first obtaining a unique serial number from the Department of Criminal Justice Information Services.
The statutory sequence is:
Obtain a unique serial number from DCJIS before manufacture or assembly.
Apply the assigned serial number during the manufacture or assembly process.
Complete the serialization according to the technical requirements.
Register the completed firearm under M.G.L. c. 140, §121B within the applicable period.
7. New Massachusetts Residents
M.G.L. c. 140, §121C provides a grace period for certain lawfully owned firearms brought into Massachusetts by a new resident.
A new resident must also separately review:
- Massachusetts firearm licensing;
- registration;
- assault-style firearm restrictions;
- large-capacity restrictions; and
- other possession laws.
8. Inherited Firearms
A firearm lawfully acquired by an heir or devisee through distribution of an estate may also qualify for a serialization grace period.
9. Dealers, Gunsmiths, Distributors, and Manufacturers
M.G.L. c. 140, §121C provides a separate period for certain firearms imported or acquired by licensed:
- firearm dealers;
- gunsmiths;
- distributors; and
- manufacturers.
10. Frames and Receivers
Massachusetts serialization requirements are particularly important for firearm frames and receivers.
A frame or receiver may itself fall within the statutory definition of firearm even if it is not attached to a complete firearm.
11. Unfinished Frames or Receivers
Massachusetts defines an unfinished frame or receiver as certain forgings, castings, printed items, extrusions, machined bodies, or similar items that:
- have reached a stage where they may readily be completed or assembled to function as a frame or receiver; or
- are marketed or sold to become or be used as the frame or receiver of a functional firearm once completed or assembled.
The statutory definition excludes components designed and intended for use in antique firearms.
12. Antique Firearms
Massachusetts' statutory definition of firearm excludes qualifying antique firearms.
Massachusetts' antique firearm definition contains exclusions involving:
- muzzleloaders incorporating firearm frames or receivers;
- firearms converted into muzzleloaders; and
- muzzleloaders readily convertible to fixed ammunition.
Review M.G.L. c. 140, §121 and GOAL's muzzleloader guidance before relying on an antique-firearm exemption.
13. Permanently Inoperable Firearms
Massachusetts' definition of firearm excludes permanently inoperable firearms as defined by law.
Do not assume that a firearm is permanently inoperable merely because it is temporarily broken, missing a part, or cannot currently be fired.
14. How Do I Get a Massachusetts Serial Number?
501 CMR 20.00 establishes the electronic request process through the Massachusetts Instant Record Check System MIRCS portal.
The regulations address:
- MIRCS account registration;
- technical requirements;
- submission of a serial-number request;
- firearm-license verification;
- issuance of the serial number;
- timing of serialization;
- application of the serial number;
- modifications during assembly;
- unused serial numbers; and
- statutory and regulatory exemptions.
15. Registration Is Separate
| Serialization | Registration |
|---|---|
| M.G.L. c. 140, §121C | M.G.L. c. 140, §121B |
| 501 CMR 20.00 | 501 CMR 19.00 |
| Concerns the firearm's identifying serial number. | Concerns entering the firearm and owner information into the Commonwealth's registration system. |
| Can apply to frames and receivers. | Can also apply to frames and receivers. |
| Separate deadlines apply. | Separate registration deadlines apply. |
16. Registration Does Not Prove Legal Possession
A firearm owner must separately determine whether the firearm may lawfully be possessed under Massachusetts law.
This can require reviewing:
- LTC or FID authority;
- assault-style firearm restrictions;
- semiautomatic firearm restrictions;
- large-capacity restrictions;
- feeding-device restrictions;
- transfer restrictions; and
- other Massachusetts firearm laws.
17. GOAL Serialization Guidance
GOAL's Chapter 135 resources separately address serialization, registration, frames and receivers, unfinished receivers, privately made firearms, muzzleloaders, assault-style firearms, and other affected firearms.
GOAL currently advises that affected firearms must comply with the serialization requirements by October 2, 2026, subject to applicable exemptions and special timelines.
Where GOAL identifies uncertainty or disagreement with state implementation, that information should be treated as GOAL legal analysis rather than as statutory text.
Serialization Checklist
Complete firearm, frame, receiver, unfinished receiver, privately made firearm, or antique.
Determine whether the firearm already has a manufacturer's, importer's, or Massachusetts-issued serial number.
Check whether the serial number satisfies applicable Massachusetts serialization requirements or qualifies for an exemption.
Existing firearm, new resident, inheritance, licensed dealer acquisition, or private manufacture.
Request a Massachusetts serial number through the state process before manufacture or assembly when required.
Follow the depth, size, location, and permanence requirements.
Determine whether the firearm must also be registered under §121B and 501 CMR 19.
Serialization does not determine whether the firearm itself is otherwise lawful to possess.
Primary Sources
- M.G.L. c. 140, §121 — Massachusetts firearm definitions, including serialization.
- Chapter 135 of the Acts of 2024 — legislation creating the current serialization framework.
- 501 CMR 20.00 — Massachusetts firearm serialization regulations.
- 501 CMR 19.00 — separate firearm registration regulations.
- GOAL — Registration & Serialization
- GOAL — Chapter 135 Definitions
- GOAL — Chapter 135 Breakdown
Massachusetts firearm laws, regulations, agency guidance, and MIRCS procedures can change. Review current Commonwealth and GOAL information before manufacturing, assembling, importing, acquiring, transferring, or possessing a firearm that may require serialization.