What is number verification and how can it be used to authenticate customers?

In practice, the digital signature It can coexist with stronger authentication mechanisms, and the number verification This scenario serves as a way to validate whether the provided number is actually linked to the mobile device the customer is using at that moment.

Instead of relying solely on passwords or SMS codes, the feature uses mobile network signals to confirm line ownership, reduce friction in the flow, and make authentication more fluid in steps such as registration, login, and transaction confirmation.

Before considering the tool itself, it's worth separating concepts. Validating the number entered in a form is not the same as confirming that the line is active, in the user's possession, and associated with the device in use. This detail changes the quality of authentication because it moves beyond the purely registration field and enters the field of proof of ownership, something relevant for operations with financial, contractual, or regulatory risk.

Summary

• Number verification validates the relationship between the number, line, and device in use.
• This feature can reduce abandonment during onboarding, login, and transaction confirmation.
• It works best as part of a layered strategy, not as an isolated defense.
• Robust workflows combine secure fallback, consent, risk analysis, and SIM swap checking.

Quick facts

• Second SerproTwo-factor authentication is already applied as an additional layer of protection for connected accounts and services.
• According to a PCDFThere was an investigated case of SIM swapping involving the use of more than 180 chips to hinder identification.
• In the guidance of PCDFPrevention includes enabling two-factor authentication, preferably without relying on a phone number.

What is number verification?

Number verification is a mobile network-based authentication mechanism that seeks to confirm whether the phone number declared by the user is indeed connected to the device used in the session. (From the public white paper...) Open GatewayThe API is presented as a mobile authentication method offering a better user experience, enhanced security, and support for registration, login, and transaction flows.

In practice, the user tends to provide less data and interact less with intermediate screens. Instead of waiting for a code to arrive via SMS, copying it, and pasting it into the app, verification can happen in the background when the technical conditions are met. CM.com describes this flow as silent authentication because much of the validation occurs on the backend, with less friction and less exposure to human error.

What does the feature actually confirm?

The central point is not to "confirm any number," but to validate ownership of that number within the context of the session. This helps in scenarios where the company needs to know if the customer is using the same phone number they registered, if the line is still valid, and if the transaction is consistent with the expected context. This is different from simply using a masked phone number field or a syntactic number validator.

Approach	What validates	Friction level	Main limitation
Format validation	If the number follows the expected pattern	Low	It does not prove ownership of the line.
OTP via SMS	Manual code receipt	Medium	Exposure to interception and SIM swapping.
Number verification	Link between line, number, and device in use.	Low	It depends on technical coverage and fallback.

This line of reasoning relates to themes discussed in authentication methods and identity validationBecause the goal isn't to replace the entire security process, but rather to make the workflow smarter. In operations with digital signature, onboarding, and acceptance, reducing unnecessary steps can increase conversion without sacrificing proper risk control.

How to use number verification to authenticate clients

The best use of number verification appears when it's integrated as a layer of the workflow, not as an isolated feature. The Open Gateway white paper lists scenarios such as registration, password recovery, quick login, and transaction validation; while idwall reinforces that onboarding and identity authentication play a direct role in fraud prevention, compliance, and reducing operational costs.

No digital onboarding

During initial registration, the feature can be activated immediately after the user provides their phone number. If the verification is successful, the company gains more confidence that the line is actually with the session holder. This reduces reliance on manual steps and helps to make the process more fluid, something consistent with customer journeys. electronic signature in digital process and with practices of digital compliance.

On recurring login

In mobile applications, number verification can serve as proof of phone line ownership to speed up access without requiring code copying. The Open Gateway document explicitly cites increased login speed and reduced manual interactions, as well as a more transparent user experience. This use is especially interesting in journeys where each extra step reduces the completion rate.

In transaction confirmation

Transfers, exchanges of registration data, acceptance of sensitive contracts, and account recovery are all instances where contextual number verification can enhance security. In the same Open Gateway material, the API is associated with protecting banking transactions and improving the conversion rate of these steps. In document operations, this can complement workflows of... signature fraud quality fraud risk analysis.

Check out these related articles as well:

• Liveness can reinforce the verification of actual presence in identity validation steps.
• Digital fraud requires context reading, history analysis, and an extra layer of authentication.
• The electronic signature API helps to integrate authentication and formalization into the same workflow.

Best practices for using the feature without creating a false sense of security.

The operational gain from number verification is real, but it does not eliminate the need for risk design. This becomes even clearer when observing the treatment given by NIST to assurance levels. According to the NIST SP 800-63BAAL2 requires proof of possession and control of two distinct factors, which shows that a single check should not be treated as a universal solution for all scenarios.

Safe fallback

Not every session will be suitable for silent validation. The device may be on Wi-Fi, the carrier may not support the expected traffic, or the application may not be able to confirm the network's technical conditions. Therefore, it's important to have a secure fallback, such as additional authentication via biometrics, passkey, authenticator app, or another layer proportional to the risk, without automatically resorting to the weakest path.

SIM swap check

If the goal is to reduce fraud, it's worth cross-referencing authentication with signs of recent SIM card replacement or suspicious line changes. The Open Gateway white paper mentions combining it with SIM swap APIs as a way to strengthen protection. This makes sense because the GSI itself notes that OTP via SMS is vulnerable to interception, including in SIM swap scams and fraudulent portability.

Consent and transparency

Since verification uses data and signals related to the mobile line, the process must be transparent to the user, with an appropriate legal basis and clear communication about the reason for the check. In legal and product teams, this connects to topics such as LGPD in digital signatures e digital signature complianceespecially when authentication influences contractual acceptance or access authorization.

Which KPIs to track in the workflow?

Without measurement, the feature becomes a vague promise. Ideally, indicators should be monitored before and after implementation, always by funnel stage and by journey type. Open Gateway highlights effects on conversion and abandonment; in the operational context, this should be translated into metrics that product, fraud, legal, and sales can read together.

KPI	What does it measure?	Practical reading
Authentication fee	Percentage of sessions successfully validated.	Shows real-time coverage of the feature.
Stream conversion	Registration, login, or transaction completed.	It indicates operational and commercial gain.
Abandonment	Users who interrupt the journey	Helps detect excessive friction.
Fraud prevented	Events banned or downgraded due to risk.	Shows the value of layered control.

Simple example of reading

1. Compare the current flow with OTP via SMS versus number verification.
2. Separate results by onboarding, login, and transaction.
3. Measure approval rates, completion time, and dropout rates.
4. Cross-reference with alerts for fraud, SIM swapping, and subsequent disputes.

If the authentication rate increases, abandonment decreases, and suspicious events don't rise, the feature tends to be adding value. If conversion improves, but disputes or post-event fraud increase, the problem isn't with the number verification concept itself, but rather with an insufficient flow design. In these cases, it's also worth reviewing the role of... facial biometrics, document analysis and contextual rules.

Real gains come from well-reviewed cash flow.

O number verification It can reduce friction, speed up authentication, and improve trust in onboarding, login, and transaction confirmations, provided it is used judiciously. It works well for validating line ownership and supporting fraud prevention, but it has technical limitations and does not, on its own, replace strong MFA, risk analysis, and ongoing governance.

In operations that aim to combine security, usability, and efficiency, you can structure this theme alongside the formalization of documentation and... from ZapSign's digital signature solution.

Frequently Asked Questions (FAQ)

Number verification replaces MFA?

Not necessarily. It can act as a relevant layer of proof of ownership of the mobile line, but MFA depends on the complete authentication design. In higher-risk scenarios, the company may need to combine number verification with another factor, such as biometrics, passkey, app authentication, or document verification, to achieve a level of assurance compatible with the operation.

Is number verification the same as OTP via SMS?

No. SMS OTP relies on sending a code for the user to read and manually enter. Number verification attempts to confirm ownership of the number based on the connection and mobile network signals, reducing steps and exposure to typing errors. Therefore, it is usually considered a more fluid option for mobile experiences when adequate technical support is available.

Does this feature alone resolve the risk of SIM swapping?

No, it doesn't. It improves the flow and helps validate line ownership within the session context, but it doesn't eliminate the need to monitor recent SIM card swaps, anomalous behavior, and other signs of fraud. In critical journeys, the recommendation is to combine authentication with SIM swap checking, risk analysis, and additional approval criteria.

At what points in the funnel does it tend to generate the most value?

The most common issues are onboarding, recurring login, account recovery, and transaction confirmation. This happens because these steps concentrate friction, abandonment, and risk. When verification reduces manual interaction without compromising security, the company tends to gain in completion time, conversion, and user experience, especially in apps and mobile-first journeys.

Which areas of the company should participate in the implementation?

Ideally, product, technology, security, legal, compliance, and operations are all considered. Product helps design the journey, technology integrates the API, security and fraud define complementary controls, and legal assesses the legal basis, transparency, and regulatory adequacy. This joint vision prevents the feature from becoming merely a UX improvement without risk mitigation or, at the other extreme, an excessive block that hinders conversion.