Short answer. Article 282 of the Labor Code names "gross and habitual neglect" as a just cause, which by its own wording requires more than one isolated mistake. But a single incident can still be a just cause on its own if it amounts to serious misconduct, willful disobedience, fraud, or breach of trust — separate grounds the same article lists.
What the law says
An employer may terminate an employment for any of the following causes: Serious misconduct or willful disobedience by the employee of the lawful orders of his employer or representative in connection with his work; Gross and habitual neglect by the employee of his duties; Fraud or willful breach by the employee of the trust reposed in him by his employer or duly authorized representative; Commission of a crime or offense by the employee against the person of his employer or any immediate member of his family or his duly authorized representatives; and Other causes analogous to the foregoing.
Labor Code, Article 282 — Just Causes For Dismissal. Read the full provision →
Why "habitual" is written into the neglect ground specifically
Article 282 lists gross and habitual neglect by the employee of his duties as one of its just causes. The word habitual is part of the standard itself — this ground, on its own terms, is not written around a single lapse but around a pattern of neglect that is both serious (gross) and repeated (habitual). A one-time mistake, evaluated only against this particular ground, does not carry the repetition the article's own wording requires.
A single mistake can still fall under a different ground
The neglect ground is only one of several the article lists. It also names serious misconduct or willful disobedience, fraud or willful breach ... of the trust reposed in him, and commission of a crime or offense against the employer or immediate family. None of these grounds carries a habitual-conduct requirement the way neglect does — a single act of serious misconduct, a single instance of fraud, or a single willfully disobedient act can each independently support termination under the article, entirely apart from whether any neglect was involved at all.
So the real question is which ground actually fits
Whether a single mistake can justify dismissal depends on which of Article 282's grounds the conduct actually falls under, not on treating "just cause" as one uniform standard. If what happened was carelessness or an oversight, the article's own language suggests it needs to be gross and habitual to qualify as neglect. If what happened instead involved deliberate defiance, dishonesty, or a serious breach of the trust placed in the employee, the article does not require repetition — the single act can be enough on its own.
What this means for evaluating your situation
The label an employer puts on the incident matters less than what actually happened and which ground it fits. A mistake framed as "neglect" but treated as grounds for immediate dismissal deserves a closer look at whether it was truly gross and part of a pattern, since that is what the article itself demands for that specific ground. If the same incident is instead characterized as misconduct, disobedience, or a breach of trust, a different — and less repetition-dependent — standard from the same article would apply.