Montana Data Breach Notification Laws: Reporting Rules & Timelines (2026)

Montana requires businesses that experience a data breach to notify affected residents without unreasonable delay under Mont. Code Ann. 30-14-1704. No fixed-day deadline applies; the standard is flexible, but the Montana Attorney General determines whether any delay was unreasonable on a case-by-case basis.

If your business stores personal information belonging to Montana residents, a data breach triggers specific legal obligations under Montana's breach notification statute. Mont. Code Ann. 30-14-1704 through 30-14-1706 sets out who must notify, what triggers the duty, and how quickly you need to act. Montana enacted its original breach notification law in 2005, and the legislature has amended it several times to expand the definition of personal information and tighten notification requirements.

This guide covers the full scope of Montana's breach notification requirements, including what personal information triggers the law, who must be notified, the timeline, penalties, exemptions, and how the Montana Consumer Data Privacy Act (MCDPA) interacts with breach obligations.

Who Must Comply With Montana's Breach Notification Law

Montana's law applies to any person or business that conducts business in Montana and owns or licenses computerized data that includes personal information. It also applies to any person or business that maintains computerized data containing personal information that it does not own. This captures both data owners and third-party service providers such as cloud hosting companies or payment processors.

When a third-party data maintainer discovers a breach, it must notify the data owner or licensee "as soon as the discovery is made." The data owner then carries the primary responsibility to notify affected consumers and the Attorney General.

Government Entities

Montana state agencies (executive and legislative branch bodies) are not covered by the business breach statute at all. They follow a separate law, Mont. Code Ann. 2-6-1501 through 2-6-1504, which similarly requires notice without unreasonable delay but also requires simultaneous notice to the state's chief information security officer. Local governments and political subdivisions are not defined as "state agencies" under that statute, and it is not clear that Montana's business breach law extends to them either. A local government entity with questions about its own obligations should consult counsel.

Insurance Licensees

Montana's definition of "business" at Mont. Code Ann. 30-14-1702(1)(b) expressly excludes "industries regulated under Title 33," the insurance code. Insurance licensees and insurance-support organizations instead follow Mont. Code Ann. 33-19-321, a parallel breach statute carrying the same "without unreasonable delay" standard and the same personal-information categories.

The difference that matters is which regulator receives the filing. Under 33-19-321(5), the simultaneous electronic copy of the notification goes to the insurance commissioner, not to the Attorney General's consumer protection office. An insurer that follows the general business track would report to the wrong agency.

What Qualifies as a Breach

Under Mont. Code 30-14-1704(4)(a), a "breach of the security of the data system" means the unauthorized acquisition of computerized data that materially compromises the security, confidentiality, or integrity of personal information maintained by the person or business "and causes or is reasonably believed to cause loss or injury to a Montana resident."

That is a two-part test, and both halves must be satisfied. Material compromise alone is not enough; the statute also requires loss or injury, actual or reasonably believed, to a Montana resident. The definition sits in the breach statute itself, not in the general definitions at 30-14-1702, which do not define the term at all and carry a different, broader "personal information" definition written for the record-destruction provisions.

Good Faith Exception

A good faith acquisition of personal information by an employee or agent of the entity does not constitute a breach, provided the personal information is not used for an unauthorized purpose or subject to further unauthorized disclosure.

Encryption

Montana's duty runs only to residents whose unencrypted personal information was or is reasonably believed to have been acquired, and 30-14-1704(4)(b)(i) reaches a name plus a listed data element only "when either the name or the data elements are not encrypted." Data that was encrypted therefore falls outside the trigger.

Montana does not define "encrypted," set an encryption standard, or address what happens when an attacker also obtains the decryption key. Many other states write an explicit key-acquisition exception into their breach statutes. Montana's does not contain one. An entity whose encryption keys were taken alongside the data should treat the question as unsettled and consult counsel rather than assume the data still counts as encrypted for purposes of the statute.

Personal Information That Triggers Notification

Montana's definition of personal information is broader than many states. Under Mont. Code Ann. 30-14-1704(4)(b), personal information means an individual's first name or first initial and last name combined with any one or more of the following:

• Social Security number
• Driver's license number, state ID card number, or tribal ID number
• Account number or credit or debit card number combined with any required security code, access code, or password that would permit access to the account
• Medical record information
• Taxpayer identification number
• Identity protection personal identification number issued by the IRS

The inclusion of medical records, taxpayer identification numbers, and IRS identity protection PINs makes Montana's definition notably broader than states that only cover financial account data and SSNs.

Personal information does not include publicly available information that is lawfully made available to the general public from federal, state, or local government records.

Notification Timeline

Montana requires notification "without unreasonable delay." Unlike states such as Indiana (45 days) or Colorado (30 days), Montana does not impose a specific day count. The standard is flexible but carries real enforcement risk if the Attorney General determines a delay was unreasonable.

When Delay Is Permitted

A delay in notification is reasonable if it is necessary to:

1. Determine the scope of the breach and restore the reasonable integrity of the data system
2. Comply with a request from law enforcement that notification would impede a criminal investigation

When a delay occurs for law enforcement purposes, notification must be made without unreasonable delay after law enforcement determines disclosure no longer compromises the investigation.

Who Must Be Notified

Affected Individuals

Every Montana resident whose unencrypted personal information was or is reasonably believed to have been acquired by an unauthorized person must be notified.

Montana does not prescribe what the notice must say. Mont. Code 30-14-1704(5) governs only the method of notice, written, electronic, telephonic, or substitute, and no subsection of the statute sets out required content. That is unusual among state breach laws, many of which mandate specific disclosures.

Because the statute is silent, notice content in Montana is a matter of practice rather than a legal requirement. Notices commonly describe the categories of information involved, give a contact for questions, and suggest steps such as reviewing account statements and obtaining free credit reports. Pointing the reader to a credit reporting agency is optional, and it carries a consequence described in the next section.

Montana Attorney General

The Montana Attorney General's Consumer Protection Office must be notified of any breach affecting Montana residents. Under Mont. Code 30-14-1704(8), the business must simultaneously submit an electronic copy of the notification to the AG's consumer protection office, along with a statement of the date and method of distribution.

This is a mandatory requirement for every breach that triggers consumer notification, regardless of the number of affected residents. Insurance licensees and insurance-support organizations are the exception: they file the same copy with the insurance commissioner under 33-19-321(5) instead.

Consumer Reporting Agencies

Under Mont. Code Ann. 30-14-1704(7), if the notice given to individuals suggests, indicates, or implies that they may obtain a copy of their file from a consumer credit reporting agency, the business must coordinate with that agency on the timing, content, and distribution of the notice. The coordination may not unreasonably delay notice to affected individuals.

This obligation is conditional and entirely within the sender's control. It attaches only because the business chose to point readers toward a credit reporting agency. A notice that says nothing about obtaining a credit file does not trigger the coordination duty at all.

How to Provide Notification

Montana permits the following notification methods:

• Written notice sent by mail to the last known address of the individual
• Electronic notice, if the notice is consistent with the federal E-SIGN Act's provisions on electronic records and signatures, 15 U.S.C. 7001
• Telephone notification

Substitute Notice

Substitute notice is available when:

• The cost of notification would exceed $250,000
• The affected class exceeds 500,000 individuals
• The entity does not have sufficient contact information

Substitute notice is not a three-part checklist. Mont. Code 30-14-1704(5)(b) joins the first two items with "and" and the second and third with "or":

1. Email notice when the entity has an email address for the subject persons, and
2. Conspicuous posting of the notice on the entity's website page, if it maintains one, or
3. Notification to applicable local or statewide media

A purely local outlet satisfies the third item. The statute says "applicable local or statewide media," not major statewide outlets.

Enforcement and Penalties

Montana's breach notification law is enforced by the Attorney General under the Montana Unfair Trade Practices and Consumer Protection Act. Violations of the breach notification statute constitute unfair or deceptive trade practices under Mont. Code 30-14-103.

The Attorney General may seek:

• Injunctive relief to stop ongoing violations
• Civil penalties up to $10,000 per violation under Mont. Code 30-14-142, if a court finds the violation was willful, or for violating an injunction
• Restitution for affected consumers

There is no private right of action for breach notification violations. Only the Attorney General can bring enforcement actions under this statute.

How the MCDPA Interacts With Breach Notification

The Montana Consumer Data Privacy Act (MCDPA), effective October 1, 2024, created a comprehensive privacy framework for Montana. However, the MCDPA does not contain its own breach notification requirements. Businesses subject to the MCDPA must still follow Mont. Code 30-14-1704 for breach notification.

The MCDPA does add relevant obligations that affect breach preparedness:

• Data security requirement: Controllers must implement reasonable administrative, technical, and physical data security practices appropriate to the volume and nature of the personal data at issue.
• Data minimization: Controllers must limit data collection to what is adequate, relevant, and reasonably necessary for the disclosed purpose.
• Sensitive data consent: Biometric data, precise geolocation, and other sensitive categories require explicit consumer consent before processing.

The MCDPA is enforced separately by the Attorney General, with civil penalties up to $7,500 per violation under Mont. Code Ann. 30-14-2820.

Do not assume a right to cure. Section 30-14-2820(2) makes a violator liable "following the 30-day period described in 30-14-2817(3)," but the current text of Mont. Code Ann. 30-14-2817, as amended in 2025, contains no cure period at all. Its subsection (3) now covers civil investigative demands. The cross-reference points at a provision that no longer exists, so a cure opportunity cannot be relied on.

This article provides general legal information about Montana data privacy laws and breach notification requirements. It is not legal advice, and it does not create an attorney-client relationship. Data breach response involves time-sensitive obligations. Consult a qualified attorney licensed in Montana for guidance specific to your situation.

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