FCC DNO Blocking Mandate: What the December Deadline Means for Your Network

FCC Deadline: The Stakes

Non-compliance carries serious consequences. The FCC can impose forfeitures of up to $23,000 per violation under 47 U.S.C. § 503(b), with each day of continuing violation constituting a separate offense.⁴ More significantly, the FCC has warned that failure to comply “may result in the blocking of all traffic from a non-compliant provider.”⁵ This means compliant downstream providers can refuse your traffic, cutting off your ability to complete calls.

Understanding DNO Blocking

A do-not-originate (DNO) list identifies phone numbers that should never be used to place outbound calls. According to the FCC, DNO lists include “numbers that are invalid, unallocated, or unused, as well as numbers that are valid but allocated for inbound calls only.”⁶

Think of toll-free numbers like 800, 888, 877, 866, 855, 844, and 833 series. These numbers are designed to receive calls, not make them. If you receive a call that appears to come from a toll-free number, something is wrong. The same principle applies to government numbers, certain emergency service numbers, and invalid or unassigned numbers.⁷

Why It Matters

Fraudsters use caller ID spoofing to make their calls appear legitimate. By spoofing numbers that shouldn’t originate calls, they evade detection and trick consumers into answering. DNO blocking prevents this by stopping calls that claim to originate from these numbers. The FCC notes that “blocking calls purporting to originate from these numbers prevents callers from using those numbers to evade detection.”⁸

The Four Required Categories

The FCC requires that DNO lists include at minimum:

1. Invalid numbers (don’t conform to valid formats)
2. Unallocated numbers (not yet assigned)
3. Unused numbers (allocated but not in service)
4. Inbound-only numbers (like toll-free numbers)⁹

By extending these requirements throughout the call path, the FCC aims to “close loopholes that bad actors exploit” and “help prevent illegal calls from reaching consumers.”¹⁰


What “Reasonable” Means

The FCC intentionally avoided mandating a specific DNO list provider. Instead, the Commission defined a “reasonable” do-not-originate list as one that includes the four categories above.¹¹ This gives you flexibility in how you meet the requirement.

You can use a single DNO source or multiple sources. The rules explicitly permit providers to “rely on a single list or multiple lists” and “combine multiple sources of information.”¹²

Your Four Core Obligations

Under 47 CFR § 64.1200(p), effective December 15, 2025, you must:¹³

1. Use at least one reasonable DNO source
2. Block calls from DNO numbers
3. Establish an error reporting mechanism (publicly available point of contact)¹⁴
4. Document your compliance¹⁵
   
   
   

How This Differs from Gateway-Only Rules

Previous rules, effective June 14, 2022, required only gateway providers to block calls using DNO lists.¹⁶ The December 15 expansion means broader scope (all providers in the call path), domestic coverage (previous rules focused on international-to-domestic calls), and multiple checkpoints throughout the network.¹⁷

FCC DNO Blocking Compliance Roadmap

Step 1: Assess Where You Stand

Evaluate your current call blocking infrastructure. Can your systems identify and block calls based on DNO lists? What modifications are necessary? Examine your existing call authentication and blocking systems, technical integration points for DNO data, and timeline constraints.¹⁸

Step 2: Choose Your DNO Source

When evaluating DNO service providers, remember the FCC’s definition of “reasonable” requires coverage of invalid, unallocated, unused, and inbound-only numbers.¹⁹ Ask potential providers about their data sources, update frequency, accuracy rates, API uptime and latency, and pricing models.

The FCC emphasized that “we allow providers to determine which list or lists to use, so long as the list includes, at a minimum, the categories of numbers we specify.”²⁰

Step 3: Integrate and Test

Technical integration varies based on your network setup but generally requires API or database connectivity to your chosen DNO source, call processing logic to query DNO data, blocking mechanisms at appropriate network points, and logging systems.²¹ Before December 15, conduct thorough testing to verify everything works correctly.

Step 4: Set Up Error Reporting

Under 47 CFR § 64.1200(p)(2), you must “establish a point of contact for a subscriber or other voice service provider to report erroneous blocking” and make this contact information publicly available.²² Create a dedicated phone number, email address, or web form with a clear investigation process.

Step 5: Document Everything

Maintain internal records showing which DNO source(s) you’re using, when you implemented blocking, testing results, where you’ve published error reporting contact information, and any blocking statistics.²³

Running Short on Time?

If December 15 is approaching quickly, immediately contact DNO service providers, focus on minimum viable compliance (at least one reasonable DNO source), conduct focused testing on critical functionality, set up basic error reporting, and document your good-faith efforts.²⁴

The Data Freshness Challenge

Phone numbers don’t sit still. The FCC recognized that “the need for DNO lists to be updated regularly to account for numbers that are reassigned or newly allocated” is critical to effective blocking.²⁵

According to industry data cited in FCC proceedings, approximately 35 million phone numbers are disconnected and reassigned to new subscribers each year in the United States.²⁶ That’s roughly 100,000 numbers changing hands every day. A number on a DNO list today might be legitimately assigned to an active subscriber tomorrow.

Static Lists vs. Real-Time Data

Traditional static DNO lists update on fixed schedules (weekly, biweekly, or monthly). The FCC record includes concerns that “stale data in DNO databases can result in blocking of legitimate calls” and that “the time lag between when a number is reassigned and when that information is reflected in a DNO database creates opportunities for erroneous blocking.”²⁷

The Commission acknowledged these concerns, stating that “we recognize that DNO lists must be kept up to date to minimize the risk of blocking wanted calls.”²⁸ While the FCC didn’t mandate real-time updates, the Commission encouraged providers to “use the most current information available” and noted that “more frequent updates will reduce the likelihood of erroneously blocking calls from recently reassigned numbers.”²⁹

The FCC stated: “We decline to mandate a specific update frequency for DNO lists. Instead, we expect providers to use DNO lists that are updated with sufficient frequency to be effective while minimizing the risk of erroneous blocking.”³⁰

Netnumber Dynamic DNO: Built for Real-Time Networks

The December 15 deadline requires action, but it also presents an opportunity to implement DNO blocking that goes beyond the suggested minimum compliance. Netnumber’s Dynamic DNO service addresses the FCC’s requirements under 47 CFR § 64.1200(p) while solving the data freshness challenge that static lists can’t overcome.

Comprehensive Coverage with Near Real-Time Updates

Dynamic DNO provides complete coverage of all required categories (invalid, unallocated, unused, and inbound-only numbers)³¹ with near real-time data updates, reflecting changes in number status within minutes to hours. This directly addresses the FCC’s concern about regular updates to account for reassigned or newly allocated numbers.³²

When a number’s status changes, whether it moves from unallocated to active or from active to disconnected, Dynamic DNO captures that change quickly. This means fewer false positives (blocking legitimate calls from recently reassigned numbers) and better detection (identifying newly compromised numbers faster).

Integration with netnumber Services Registry

Dynamic DNO integrates with the netnumber Services Registry (nnSR), North America’s authoritative registry for text-enabling 10-digit and toll-free numbers. This integration is particularly important because the FCC extended DNO blocking requirements to SMS and text messaging under 47 CFR § 64.1200(p).³³

The Commission stated that “we extend our Do-Not-Originate blocking requirements to apply to text messages” to address SMS-based schemes and spoofing.³⁴ With Dynamic DNO’s nnSR integration, you get comprehensive coverage for both voice and messaging through a single solution.

Designed for Quick Deployment

With December 15 approaching, implementation speed matters. Dynamic DNO’s API-based architecture enables deployment in days or weeks rather than months, depending on your system architecture. The flexible integration options support rapid compliance.

Dynamic DNO uses intelligent logic to improve accuracy beyond simple list matching, considering timestamps showing when numbers were reported, multiple reports that reset timestamps to the most recent, and signals indicating when numbers are no longer relevant for blocking. This smart logic approach, combined with near real-time updates, helps minimize erroneous blocking while maintaining effective protection.³⁵

To understand how Dynamic DNO can help your network meet the December 15 deadline while building a foundation for ongoing compliance, visit netnumber.com/dynamic-dno or contact our team.

For organizations focused on broader telecommunications security, our Fraud Prevention Registry (FPR) complements DNO blocking by enabling real-time sharing of intelligence across carriers and enterprises.

>>> Frequently Asked Questions <<<

What is the December 15, 2025 FCC deadline?

December 15, 2025 is the effective date for new FCC rules under 47 CFR § 64.1200(p) requiring all voice service providers to block calls purporting to originate from numbers on a reasonable do-not-originate list.³⁶

Who must comply?

All voice service providers, including intermediate providers and terminating providers.³⁷ The FCC defines “voice service provider” broadly to include both facilities-based and non-facilities-based providers.³⁸

What makes a DNO list “reasonable”?

A reasonable DNO list must include invalid numbers, unallocated or unused numbers, and numbers allocated for inbound use only (like toll-free numbers).³⁹

Can I use multiple DNO sources?

Yes. The FCC explicitly permits providers to use multiple DNO list sources and combine information from different sources.⁴⁰

Does DNO blocking apply to text messages?

Yes. The FCC’s rules apply DNO blocking requirements to both voice calls and text messages under 47 CFR § 64.1200(p).⁴¹

What happens if I miss the deadline?

Missing the deadline risks FCC enforcement action, including potential monetary forfeitures and the possibility that compliant downstream providers will block all traffic from your network.⁴²

Moving Forward

The December 15 deadline represents more than a compliance checkbox. It’s an opportunity to strengthen your network’s defenses against illegal robocalls and caller ID spoofing while protecting your customers and your business.

For help navigating the technical and compliance aspects of DNO blocking, netnumber’s team brings decades of telecommunications expertise and solutions built specifically for these Netnumber’s netnumber’s challenges. Learn more about Dynamic DNO and how we can help you meet the December 15 deadline with confidence.