Segregation of Duties (SoD)

If one employee can create a new supplier, approve an invoice from that supplier and release the payment, the organization is relying entirely on that person's honesty and accuracy. A mistake would go unnoticed, and a fraud would be easy to hide. Segregation of duties prevents this by splitting sensitive tasks so that at least two people are involved. One person sets up the supplier, another approves the invoice and a third releases the payment. Each step becomes a check on the others, and wrongdoing would require collusion. Collusion is harder to arrange and more likely to be discovered.

Segregation of duties is one of the oldest and most widely used internal controls. It is a basic expectation of auditors, a common focus of SOX testing and a key design principle in finance systems and ERP platforms. It also applies in technology, where developers should not be able to move their own code into production without review. The term separation of duties is often used for the same idea. For finance, risk, audit and IT teams, SoD is essential to preventing fraud and errors, but it has to be balanced against practical limits in smaller teams.

Definition of Segregation of Duties

Segregation of duties is the assignment of incompatible responsibilities, typically authorizing transactions, recording them, holding custody of the related assets and reconciling the results, to different people or roles, so that no individual controls a transaction from start to finish.

It is a core preventive control within internal controls, is often enforced through system access managed by IT general controls and is commonly documented in a risk control matrix.

The Four Functions to Separate

Authorization is approving a transaction, such as signing off a purchase order or a journal entry.

Recording is entering the transaction in the books or systems, such as posting an invoice.

Custody is having control of the related assets, such as cash, inventory or the ability to release payments.

Reconciliation or verification is checking that records match reality, such as comparing bank statements with the ledger.

Ideally, no one person performs more than one of these functions for the same transaction. Where that is not possible, the most important separation is usually between authorizing a transaction and holding custody of the related asset.

Common SoD Conflicts

In procure-to-pay, conflicts include creating suppliers and approving payments to them, or entering invoices and releasing payments.

In payroll, conflicts include adding employees and approving pay runs.

In the general ledger, conflicts include creating and approving the same journal entries.

In IT, conflicts include developing code and deploying it to production, or administering security settings and reviewing their own access.

These combinations of access are sometimes called toxic combinations, and SoD rule sets in ERP and identity tools are designed to detect them. A rule set lists each pair of permissions that should not be held by the same user.

Importance of Segregation of Duties in Risk and Compliance

Segregation of duties prevents fraud. Requiring more than one person for sensitive transactions makes fraud harder to commit and much harder to hide.

It catches errors. A second person reviewing or completing a step is more likely to spot mistakes before they affect financial records or customers. Even honest, careful staff make mistakes, and a second check catches many of them.

It also satisfies auditors and regulators. Weak SoD is one of the most common causes of control deficiencies and, in serious cases, material weaknesses under SOX.

Segregation of Duties and Financial Management

Many occupational frauds, such as billing schemes, fake suppliers and payroll fraud, depend on one person controlling several steps of a process.

SoD controls over procure-to-pay, payroll and journal entries protect the integrity of financial statements.

Remediating SoD conflicts in ERP systems after an audit finding can be expensive, so designing roles correctly from the start saves money.

Adding staff only to separate duties is costly, which is why smaller teams often rely on compensating controls instead. Using system-enforced roles is usually cheaper than relying on manual checks.

Common Challenges

Small teams may not have enough people to separate every incompatible duty. A finance team of two or three people cannot split every task the way a large department can.

Access tends to accumulate as people change roles, creating conflicts that nobody intended. Without regular reviews, long-serving employees can end up with far more access than their current job requires.

Emergency or administrator access can bypass SoD unless it is tightly controlled and reviewed.