Retaliation claims are among the most common employment claims and among the most winnable, because they do not require the underlying complaint to have been correct.

The usual structure has three elements: the employee engaged in protected activity, suffered an adverse action, and there is a causal connection between them.

Protected activity is broader than people expect. Filing a charge is obvious; so is complaining internally about conduct the employee reasonably believes is unlawful, participating in someone else’s investigation, or requesting an accommodation. The belief need only be reasonable — an employee whose discrimination complaint is ultimately unfounded is still protected from being punished for making it.

Adverse action is also broader than termination. Anything that would dissuade a reasonable worker from complaining can qualify: a demotion, a schedule change, exclusion from meetings, a sudden negative review after years of good ones.

Causation is usually proved by timing and by change. An employee with five years of strong reviews who is written up twice in the month after complaining has a case built almost entirely from the employer’s own documents.

The lesson for employers is that the response to a complaint is more likely to create liability than the complaint itself. Once a complaint is made, every subsequent decision about that employee needs a documented, independent reason.