This may be the most difficult category of just cause for the employer to prove. Generally, courts are sympathetic to employees whose performance is being criticized.

There is a heavy onus on the employer to prove that the employee's performance is so poor as to brand the employee as "incompetent" and deny that employee a severance payment. If the court determines that an employee is trying to perform well at his or her job, and is unable to succeed due to lack of ability, then the court will be reluctant except in the most extreme cases of incompetence, to find that the employer has established just cause.

Even for those situations where an employee may in fact be incompetent, the employer is generally required to warn the employee in clear terms as to what areas require improvement, and the employer is also required to make it clear that failure to rectify the deficient area may result in termination of employment.