Reasons an Employer Can Lawfully Pay Two People Differently

The burden is the first thing to understand

Before the defenses themselves, notice who has to establish them. Once an employee shows that they are paid less than a comparator of the opposite sex for equal work, the burden shifts to the employer to prove the difference falls within one of the four exceptions. This is an affirmative defense rather than something the employee must disprove.

That structure matters more than most of the doctrine. It means an employer who cannot articulate a documented reason for a pay difference is in a losing position rather than a neutral one, and it means the practical question in any dispute is not “can I prove discrimination” but “can they prove a defense”. Those are very different bars and the second is higher than employers often expect.

The first three, and why they rarely decide cases

A seniority system justifies paying a longer-serving employee more, and it is straightforward when it is real. What makes it real is that it exists as a system — applied consistently, known to employees, and operating by defined rules rather than by an after-the-fact observation that one person happened to arrive earlier. An employer producing a seniority explanation only once a complaint has been made is producing a rationalization rather than a system.

A merit system works the same way and fails the same way. It requires genuine, documented performance evaluation applied consistently across the people being compared. Where an employer has performance ratings on file for both employees, made contemporaneously against known criteria, the defense is strong. Where the merit judgment lives in a manager’s recollection, it is not a system at all.

The third defense covers systems measuring earnings by quantity or quality of production: piece rates, commission structures, output-based schemes. It is the narrowest of the four and by some distance the least argued about. A commission structure either applies to both people on the same terms or it does not, and that is a matter of record rather than of interpretation. Where it does get litigated, the dispute is usually about territory or account allocation rather than about the scheme itself.

The fourth defense, where the cases live

The fourth defense is any factor other than sex, and its sheer breadth is why it carries almost all the weight. Education, training, experience, geography, shift, the demands of the labor market at the moment each person was hired, and a great deal else can all qualify in principle. Two conditions constrain it: the factor must be job-related or serve a legitimate business purpose, and it must actually explain the difference rather than merely existing alongside it. The second condition is where most defenses fail.

Courts have been increasingly demanding about that second condition. An employer pointing to a factor has to show it was actually relied upon, not that it could in principle have justified the decision. “He has a degree” is not a defense if degrees were not part of how anybody’s pay was set, and an employer producing a list of differences between two employees is not thereby producing an explanation.

The market-demand version deserves particular attention because it is common and genuinely contested. An employer arguing that one hire cost more because the market was tight that quarter is making a real argument that can succeed, and it is also the argument most easily used to launder something else. What separates the two is documentation made at the time rather than reasoning assembled later.

Prior salary is increasingly excluded

The most significant movement in this whole area concerns whether prior pay can count as a factor other than sex. The argument against allowing it is straightforward and has proved persuasive. If pay differences already exist in the market, then setting new pay from previous pay imports those differences into every subsequent job. The defense would then permit an employer to perpetuate a gap it did not create, indefinitely, while never making a decision anybody could point at.

A substantial number of jurisdictions have now foreclosed this. Some do it through salary history bans that prohibit asking at all, some through equal pay statutes that expressly exclude prior salary from the permitted factors, and several do both. A middle group allows prior pay to be considered only in combination with other factors, and another allows it only where the candidate volunteered the information without being asked. Those distinctions matter enormously in practice and are easy to miss in a summary.

Because the position varies substantially by state and has been moving steadily in one direction for several years, this is the point where any national summary is least reliable, including this one. If prior salary is the explanation you have been given for a pay difference, your state’s rule is the thing to look up before anything else. It is a quick lookup and it can settle the question outright.

What states have tightened beyond the federal floor

Several states have narrowed these defenses in ways that change outcomes. Some require that the factor relied upon be job-related and consistent with business necessity rather than merely being a factor other than sex. Some require the employer to show the factor accounts for the entire difference rather than some of it. Some require that reliance on the factor be reasonable and that no less discriminatory alternative was available.

Each of those is a meaningfully higher bar than the federal standard. Where a state has adopted them, the analysis under state law can produce a different answer from the federal analysis on identical facts, which is not a contradiction but two tests with different thresholds. As everywhere else in wage law, the more protective rule governs, so it is worth running both.

Two things that are not defenses

The first is that the employer did not intend to discriminate. Federal equal pay law does not require intent, so an unequal outcome produced by an unexamined process is not excused by the absence of anybody deciding to do it. That is a deliberate feature rather than an oversight, because intent is nearly impossible to establish and pay systems drift on their own.

The second is that the employee agreed to the pay. Consent is not a defense to an equal pay claim, an employee cannot waive the entitlement, and having signed an offer letter at a given figure does not settle whether that figure was lawful. That surprises people, and it is the same principle that runs through minimum wage and overtime law.

What this means practically

If you have been told why you are paid less than a comparator, the useful test is whether the reason is a system or an observation. A seniority policy, a documented merit process, a published commission scheme — those are systems. “He negotiated harder” and “he had more experience” are observations, and an observation only becomes a defense when the employer can show it was the actual basis for the decision at the time.

Ask for the reason in writing rather than accepting it in a conversation. An employer with a genuine system can produce one easily, because the system already exists in a document somewhere. An employer without one tends to produce something that does not survive being written down, and that difference is informative whatever happens next.

This is general information about how the defenses work rather than legal advice about your situation. State law varies substantially and is often more protective than federal law, so an employment lawyer or your state agency is the place to test a specific set of facts — and there are deadlines, so it is worth asking sooner rather than later.