Separation of duties (SoD) is an internal control that divides incompatible responsibilities among different people or roles, so one person cannot control every critical step in a transaction or system process. Also called segregation of duties, it is used to reduce the risk of error, fraud, waste, and misuse of authorized access—not to guarantee those outcomes can never occur.
What is separation of duties?
Separation of duties means distributing related responsibilities so that a single person cannot authorize, carry out, record, and independently review the same activity—or otherwise control all the key stages. In a financial process, those stages can include authorization, processing and recording, review, and custody of related assets. In information security, the same principle applies to system privileges: a user should not have enough access to misuse a system alone.
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Accounting and audit sources often use segregation of duties; information-security sources also use separation of duties. The terms refer to the same broad control principle here. When following a particular framework, use its terminology.
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Dividing responsibilities reduces opportunities for mistakes, waste, fraud, or abuse of authorized privileges. It also creates a check: another person or group handles a related step, increasing the chance that an error or wrongful act will be noticed. The U.S. Government Accountability Office (GAO) describes the principle this way: “Key duties and responsibilities need to be divided or segregated among different people to reduce the risk of error or fraud.” (GAO, Standards for Internal Control in the Federal Government.)
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Separation lowers risk; it does not eliminate it. People may collude, reviews may fail, and controls may not operate as intended. GAO treats segregation as one activity within a broader internal-control system, alongside procedures, supervision, review, and evidence that controls were performed.
Examples of incompatible duties
Accounting and financial transactions
For a transaction, approval should be separated from processing and recording where the risk warrants it. Payment or receipt of funds can also be separated from review, and custody of an asset from maintaining its records. These divisions make it harder for one person to initiate and conceal an improper transaction. GAO’s Internal Control Management and Evaluation Tool describes these transaction stages.
Payroll
The person authorizing a paycheck should not also be able to prepare it without an independent check. NIST’s glossary uses payroll as an example of separation of duty (NIST CSRC glossary: Separation of Duty).
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System roles can be divided so that access-control administration is separate from audit administration. Depending on the organization’s risks, programming, configuration management, quality assurance, testing, and network security responsibilities may also need to be divided. NIST’s Special Publication 800-171 Revision 3 addresses separation of duties and access authorizations, including conflicts that cross systems or application domains.
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Two-person operations
A two-person rule requires a second authorized person to be different from the person who began an operation. This is a dynamic check: the system verifies the identities of participants when the operation occurs, rather than relying only on restrictions imposed when roles are assigned. NIST describes static and dynamic enforcement in its glossary entry.
These examples are not a universal role matrix. Which duties conflict depends on the process, assets, system, and risk. GAO’s Federal Information System Controls Audit Manual (2024 revision) calls for identifying incompatible duties and mitigating risks where they cannot be segregated.
How to implement separation of duties
- Map the process. List the steps, people or roles involved, relevant assets and systems, and the decisions or records each person can control.
- Identify conflicts. Decide which combinations of approval, processing, recording, review, audit, and custody could let one person make and conceal an error or misuse. Document the incompatible duties and review the list periodically, as GAO’s 2024 audit manual recommends.
- Assign responsibilities apart. Divide conflicting duties among different people or organizational units, matching the division to the process and its risks. Different units can provide separation where assigning separate individuals within one team is impractical.
- Set system authorizations. Define access rights to support the division. Check for conflicts across related systems and application domains, not just within one application, as described in NIST SP 800-171 Revision 3.
- Choose an enforcement method. Static enforcement prevents a user from being assigned conflicting roles. Dynamic enforcement checks who is performing an operation at access time; requiring a distinct second authorized person is one example. The appropriate method depends on the process and the available system controls (NIST CSRC glossary).
- Mitigate conflicts that cannot be split. If staffing, system design, or operational needs prevent full separation, define and operate other controls that reduce the risk. GAO’s 2024 audit manual specifically addresses mitigating risks from duties that cannot be segregated.
Separation of duties versus risk mitigation
Prevention and mitigation are related but distinct. Separation assigns incompatible duties to different people or units before a transaction or system operation takes place. Mitigation addresses the remaining risk when that split is not feasible. The choice should reflect the organization’s risks and applicable requirements; the GAO and NIST materials cited here are authoritative in their stated contexts, not a universal compliance role matrix.
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|---|---|---|
| Static enforcement | Prevents a user from holding conflicting roles when roles are assigned. | When role assignments can be restricted in advance. |
| Dynamic enforcement | Checks identities or authorization at the time of access or operation. | When the control must be verified for a specific operation, such as a two-person rule. |
| Risk mitigation | Adds other controls when duties cannot be fully separated. | When staffing, system design, or operational constraints prevent a complete division. |
How to judge whether a control is effective
A written policy alone does not provide separation. The organization needs procedures and access settings that make the division real, plus supervision or review and evidence that those controls operated. The appropriate design depends on the risk: a small organization may not be able to assign every stage to a different person, while a complex system may need restrictions that span several applications. Identify the conflict first, then decide whether to separate the duties or reduce the risk with another operating control.
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