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What is the three lines model and what is its purpose?

By Kinza Yasar

The three lines model is a risk management approach to help organizations identify and manage risks effectively by creating three distinct lines of defense.

Also known as the three lines of defense model, the three lines model was originally defined by the Institute of Internal Auditors. The IIA based the model on the idea that three lines of defense work together to provide structure around risk management and internal governance. The model clearly defines roles, including oversight by a governing body, senior management and independent assurance.

This model applies to all organizations and aims to serve the following purposes:

Breaking down the three lines of defense (3LoD)

The three lines defense model is widely acknowledged as the governance model of risk. It uses a comprehensive approach to manage risk. Its implementation varies among industries and by company sizes.

Business units, compliance, audit and other risk management employees are among the groups that make up the three lines of defense and each has a specific function. Here is a breakdown of the three lines:

First line of defense: Management

Management, department or process owners -- or anyone on the front lines -- are the first line of defense. Their primary responsibility is to control and take ownership of risks associated with daily activities. They also execute risk controls, develop internal policies, own processes, supervise employee policy execution and monitor risk factors with decisions and actions.

Second line of defense: Risk management and compliance

The second line of defense provides oversight and support to the first line. It includes risk management compliance areas, such as a risk manager, compliance officer or information security officer.

The second line of defense is responsible for implementing the company's risk management program and monitoring the process and application of these policies. Managers involved with the second line also identify emerging risks within the daily operation of the business.

Third line of defense: Internal and external audits

The third line of defense includes both external and internal auditors. Their main responsibility is to ensure the effectiveness of the first and second lines of defense. This line of defense also reviews and evaluates the design and execution of the risk management program. Internal auditors typically report to the board, regulators and external auditors about the company's risk management design and operation.

Key roles in the three lines model

The three lines of defense model establishes a clear division of roles and responsibilities for accountability and transparency. The IIA lists four key roles in the model, along with the breakdown of responsibilities in each role. Organizations often differ in their distribution of responsibilities, but, according to the IIA, the following are high-level overviews of each area.

The governing body

This group accepts responsibility for managing the organization on behalf of the stakeholders. Its responsibilities include the following:

First-line management roles

First-line management roles lead and direct all actions of the plan, including managing risks and applying resources to the risk goals of the organization. Responsibilities include the following:

Second-line management roles

The second-line defense management offers support and expertise to monitor any risk management. Responsibilities include the following:

Third line of defense: Internal and external audit roles

Internal auditors have primary accountability for risk management to the governing body. Responsibilities include the following:

External auditors provide additional assistance to protect the interests of the stakeholders and ensure regulatory compliance. Responsibilities include the following:

Relationships between the 3LoD roles

The relationships between the roles in the three lines of defense model are built on collaboration, oversight and independence. Each line plays a distinct part but interacts closely to ensure risk management and governance function effectively. The three lines interact with each other in the following ways:

First line interactions

Second line interactions

Third line interactions

Besides the three lines, the governing body maintains communication with all three lines to monitor risk management activities, receive assurance reports and provide strategic direction. This oversight ensures that the organization operates within its defined risk appetite and achieves its objectives.

6 guiding principles of the three lines model

To optimize the effectiveness of the three lines model, organizations should adopt a principle-based approach. The IIA lists these six principles to guide an organization's three lines model for risk management:

  1. Governance. This gives accountability to the stakeholders and structures the organization's leadership and integrity. The organization can make risk-based decisions for the health of the organization and its stakeholders. Using recommendations from the internal audit function helps encourage the ongoing development of these risk management procedures.
  2. Governing body. This group ensures that the necessary procedures and frameworks are in place to safeguard the interests of the stakeholders. It also makes sure that moral, ethical and legal standards are upheld.
  3. Management and first- and second-line roles. The first-line roles ensure products or services are delivered safely to the customers. The second line helps manage the risk by offering expertise and monitoring and managing any regulatory issues or unethical behavior. The second line offers a broader responsibility, such as enterprise risk management, but the first line is responsible for managing the risk at a higher level.
  4. Third-line roles. Internal audit gives an objective assurance that risk management initiatives are effective. Internal auditors use independent systems and expertise to review risk management processes. The third line reports findings to management and the governing body to make any needed improvements.
  5. Third line independence. Internal audit is an independent body that provides credibility and authority to its findings. Internal audit isn't associated with management so it can provide findings that are free from bias to prevent any interference in organizational planning.
  6. Creating and protecting value. The main goal of all these roles working together is to prioritize the stakeholders' interests. They align activities through cooperation and communication. All risk-based decisions should be transparent and reliable with the alignment of these areas.

Benefits of the three lines model

The three lines model helps organizations proactively manage and address risks with enhanced governance and resilience. This model helps an organization establish a foundation for growth and success. Some of the key advantages of this model include the following:

Challenges with the model's effectiveness

There are numerous benefits to the three lines model, but there are also some challenges and potential drawbacks. Organizations can address these challenges with careful planning, continuous communication and training.

Some of the three lines model effectiveness challenges include the following:

The future of the 3LoD model

The three lines of defense model is continuously evolving to remain relevant in a rapidly changing risk landscape. Some key trends shaping its future include the following:

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08 Aug 2025

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