Whether focused on supplier oversight, certification requirements, or internal performance improvement, organizations depend on audits to maintain quality and compliance. However, the type of audit an organization chooses can significantly impact the scope and outcome of the evaluation. As such, understanding the differences between first, second- and third-party audits is essential for maximizing their value.
What Is an Audit?
ISO 19011 defines an audit as a “systematic, independent and documented process for obtaining audit evidence and evaluating it objectively to determine the extent to which the audit criteria are fulfilled.” While all audits share this fundamental purpose, they are generally categorized into three types: first-party, second-party, and third-party audits.
What Is a First-Party Audit?
A first-party audit, commonly known as an internal audit, is conducted by the organization itself. Internal audits are performed to determine whether management systems, processes, and operations conform to established requirements and organizational objectives.
These audits may be conducted by trained employees, internal audit teams, or external consultants acting on behalf of the organization. The key characteristic is that the audit is performed for the organization’s own purposes.
Benefits of First-Party Audits
- Identify process inefficiencies and risks
- Verify compliance with internal policies and procedures
- Assess readiness for external audits
- Support continual improvement initiatives
- Strengthen management system effectiveness
For organizations implementing standards such as ISO 9001, ISO 14001, ISO 45001, ISO/IEC 42001, and ISO/IEC 17025, regular internal audits are a fundamental requirement for maintaining compliance and improving performance.
What Is a Second-Party Audit?
A second-party audit is an “external party” audit, meaning the evaluation is conducted by one organization on another. The most common second party audit is the supplier audit: a systematic evaluation of a vendor’s facilities, operations, and processes.
Second-party audits are commonly performed by customers or clients to ensure that products, services, or processes meet contractual requirements and quality expectations. They help verify that an organization’s suppliers and business partners have the capacity, high performance, and stability required to deliver products and services in accordance with agreed standards, requirements, and specific criteria. For example, a manufacturer may audit a component supplier to ensure the supplier maintains adequate quality controls, follows regulatory requirements, and consistently delivers conforming products.
Advantages of Second-Party Audits
- Improved supplier relationships
- Increased visibility into supplier operations
- Reduced risk of nonconforming products or services
- Enhanced supply chain resilience
- Greater assurance of contractual compliance
As global supply chains become increasingly complex, second-party audits have become an essential tool for managing quality and risk. They help organizations gain confidence in their supply chains while reducing operational, financial, and reputational risks. As part of a risk management strategy, an organization may audit a prospective partner to verify that it operates in accordance with the standards and practices expected of a project partner.
What Is a Third-Party Audit?
A third-party audit is conducted by an independent organization that has no direct relationship with either the customer or supplier. These audits are typically performed by certification bodies, accreditation bodies, or regulatory agencies. Third-party audits or assessments are often used to determine whether an organization conforms to the requirements of a specific standard, regulation, or certification program.
These audits often support certification efforts for internationally recognized management system standards, including ISO 9001 for quality management, ISO 14001 for environmental management, ISO 45001 for occupational health and safety (OH&S), ISO/IEC 27001 for information security, and ISO/IEC 42001 for artificial intelligence management systems (AIMS). Additionally, third-party assessments verify compliance with accreditation standards such as ISO/IEC 17020 (inspection bodies), ISO/IEC 17025 (testing and calibration laboratories), and especially ISO/IEC 17043 (proficiency testing providers).
Successful completion of a third-party audit or assessment can result in certification, accreditation, or continued registration, providing independent verification of an organization’s commitment to meeting established requirements. If the organization successfully demonstrates conformity, it may receive certification or maintain an existing certification/accreditation.
Benefits of Third-Party Audits
- Independent and objective assessment
- Increased credibility with customers and stakeholders
- Recognition through certification
- Enhanced market competitiveness
- Greater confidence in management system effectiveness
Because third-party auditors are impartial, their findings often carry significant weight with regulators, customers, investors, and other interested parties.
Comparing 1st, 2nd, and 3rd Party Audits
| Audit Type | Who Conducts It? | Primary Purpose |
| First-Party Audit | The organization itself | Internal evaluation and improvement |
| Second-Party Audit | A customer or business partner | Supplier or contractor assessment |
| Third-Party Audit | Independent certification body, accreditation body, or regulator | Certification, accreditation, registration, or compliance verification |
Each audit type serves a unique purpose, but together they create a comprehensive framework for quality assurance, risk management, and continual improvement.
Why All Three Audit Types Matter
Organizations often encounter all three types of audits throughout their operations. Internal audits help identify issues before they become larger problems. Supplier audits strengthen supply chain performance and reliability. Independent certification/accreditation audits provide objective verification that systems meet recognized standards.
When used effectively, these audits work together to improve organizational performance, enhance customer confidence, reduce risk, and support long-term business success.
Learn More about Audits
In the ANAB webinar “Inside the Audit: Decoding 1st, 2nd & 3rd Party Audits,” Deanne Emory provided a practical and structured overview of how these audit types function individually—and how they work together to support a mature audit program. You can watch this free ANAB webinar among others on ANAB’s YouTube Channel.
Preparing for Any Audit
Regardless of the audit type, successful preparation typically includes:
- Maintaining accurate and up-to-date documentation
- Ensuring employees understand relevant procedures
- Conducting regular internal assessments
- Addressing nonconformities promptly
- Keeping records organized and accessible
- Fostering a culture of continual improvement
For professionals looking to strengthen their auditing knowledge and skills, ANAB offers a variety of training courses covering audit principles, management system standards, supplier auditing, and auditor competency development.