Most people never think twice about whether they take a receipt when grabbing food at McDonald’s. But according to former employees, this simple habit could change the way your order is prepared and how staff treat you.

The secret lies in something called “mystery shoppers.” McDonald’s, like many other fast-food chains, hires people to secretly evaluate their restaurants. These mystery shoppers are required to ask for receipts, since it’s the only way to prove the exact time of their visit and what they ordered.

Because of this, when a customer asks for a receipt, employees sometimes assume they might be a mystery shopper. And that’s when things change. Workers suddenly pay extra attention:

• Your food is often made fresher.
• Your order is handled more carefully.
• Service might be quicker and friendlier.

In other words, simply asking for a receipt could mean you get the “best version” of McDonald’s—hot fries, fresh burgers, and efficient service—without spending an extra cent.

While not an official policy, this little insider trick has been confirmed by many who worked behind the counter. So next time you’re at McDonald’s, remember: three simple words—“Can I get a receipt?”—might make all the difference in your meal.