Untracked, unlimited PTO is all the rage these days as an attractive benefit to woo top talent. After all, who wouldn’t want to take off as much time as they want, no questions asked? (Woohoo, two-day workweeks for all!) But does untracked, unlimited PTO really benefit employers or employees?

The answer might be “neither.”

In theory, untracked, unlimited PTO seems like a great idea. Employees take the time they need to feel refreshed—whether it’s more or fewer hours than the old vacation policy—so they’ll work 100 percent when they are at their desks. This should lead to increased morale and productivity, right?

In theory. But in reality, a free-for-all PTO policy leads to employees taking fewer days off. Sure, some employees will go full month-long Tahitian holiday, but without guidelines, most employees aren’t sure how much PTO they should take. They fear that, even though no one is tracking their PTO, their managers are still judging them by their time away from their desks. What happens if they take more PTO than other employees, or more than their managers think they should? And if they have so much free time, is their job even necessary to the business at all? This leads employees to err on the side of “looking good” by taking less PTO than before, even if it impacts their wellness.

Untracked, unlimited PTO can lead to burned out employees not taking the vacations they need: the opposite of the plan’s intent. And this makes sense. After all, how can an employer know if the new unlimited vacation policy is better than the old one unless they’re actually tracking the PTO? There is wisdom in test-driving an unlimited vacation policy, but still measuring outcomes like time taken versus productivity to see how it’s working in practice.

So what are some guidelines to give this plan its best chance? For starters, planning ahead and communicating are key. Time off should still be scheduled in advance, so that managerial duties or other coverage can be arranged in the employee’s absence. It’s also wise to plan PTO days around key meetings or events so that the employee can attend. (And in many PTO plans, managers still need to approve time off, even if it is unlimited!) Some guidelines say to maintain business flow, employees should take off no more than three weeks at any one time.

In summary, untracked, unlimited PTO can seem like a great idea. It’s definitely less paperwork to worry about. But where you’d think it would mean productive, vacationed employees, the opposite is often true, so much that several successful companies have already abandoned their free-for-all PTO in favor of tracked plans. It’s not to say employers shouldn’t consider unlimited PTO—it is an attractive recruitment tool!—but they should certainly measure outcomes to see how it’s working, and they should plan ahead and communicate to ensure business needs are being met and employees are taking the vacation time they need to feel refreshed.