Telework as a reasonable accommodation seems to be a trend. Except when it’s not.

An employer has a policy that permits employees to work remotely one day every two weeks. An employee with a disability (PTSD and anxiety disorders) requests to work remotely twice per week and work weekends to make up for any lost time.

That seems like a reasonable accommodation.

Or not so much, according to a recent Tenth Circuit Court of Appeals opinion. I’ll explain to you why.

According to the opinion, the employer didn’t just reject the employee’s request and stop there. Instead, it offered the employee several options. It allowed the employee to telework one day per week even though office policy permitted only one telework day every two weeks. It also eliminated the employee’s air travel—a function which it deemed nonessential to his job. And it provided the employee with a noise-canceling headset and sent employees an email reminding them to follow office etiquette and reduce noise levels around cubicles. (The employee rejected other measures the employer offered to reduce office-related stress, including moving his cubicle to a less-trafficked area, raising the walls on his cubicle, and allowing unpaid wellness breaks.)

But, let’s focus on the remote work. Why not just let the employee telework two days a week instead of one?

The issue is whether his presence in the office at least four days a week constituted an essential function of his job. And in this particular instance, the employer was able to show that it was.

Indeed, one of the employee’s core responsibilities was conducting fraud investigations, which requires access to case files. And the case files only existed in paper form. The evidence also showed that even if the employee took the time to scan a few case files before a remote-work day, he would be unprepared to assist law-enforcement partners with questions on cases for which files had not been scanned. Ultimately, there was not enough remote work to occupy more than one day a week without compromising the employer’s mission.

So two days of remote work creates an undue hardship. Employer wins.

But, how could things have gone badly for the employer here?

Physical presence in the office does not become an essential function just because an employer says so. Likewise, an employee’s subjective beliefs about what accommodations will work for him won’t carry the day — unless he can demonstrate that essential functions are not generally job-related, uniformly enforced, or consistent with business necessity. But without such evidence, courts generally defer to an employer’s judgment about whether a function is essential.

One of the best ways to memorialize essential job functions is in a job description. Bonus points if that job description accurately reflects, well, the job description. (Perhaps your managers and employees themselves can provide input on that.) Even better, give that job description to your employee and have them sign off on it.