When planning a trip, travelers tally up all the major expenses — plane tickets, rental car, hotel, dining. But there’s one expense some vacationers overlook: tipping hotel housekeepers.

Unlike a restaurant server or the hotel parking valet, where face-to-face interaction between guests and the staff prompts a tip for a service, hotel housekeepers usually work sight unseen.

This might be why a Cornell University study found that respondents don’t feel obligated to tip hotel housekeepers, compared to bartenders or hotel bell staff. But tipping these essential hotel staff members is an important part of travel etiquette to factor into your next trip.

Here’s what travelers need to know about tipping hotel housekeeping staff, whether they enter your room or not.

Guide to tipping hotel housekeeping staff

There’s no hard-and-fast rule on how much to tip hotel housekeeping, but there are best practices you can adhere to when it comes to expressing your gratitude.

The recommended tipping range

The American Hotel & Lodging Association suggests leaving a $1-to-$5 tip per day for the housekeeping staff. The tipping range is helpful when estimating your trip budget, but how much you should ultimately tip depends on a few factors (more on this later).

When to tip your hotel housekeeper

Some guests leave a lump-sum tip on the last day of their stay, but a better practice is doling out incremental tips daily, as hotel housekeepers might have different day-to-day room assignments. A daily tip more closely ensures your gratitude goes to the specific worker who services the room each day.

Cash is king

When leaving hotel housekeeping tips, cash is preferred. Other forms of gratuity — like food, leftover alcohol or gambling tokens — may be a well-meaning gesture. However, some hotel policies restrict what housekeeping staff can accept.

For example, if you're staying at a Las Vegas hotel, you might be tempted to leave casino chips or an electronic slot machine voucher as a tip for housekeeping, but state gaming regulations prohibit housekeepers from accepting them. Further, some hotels have strict no-gambling policies for their staff, which puts housekeepers in a difficult position when redeeming vouchers or casino chips for cash.

How to leave tips for housekeeping

Make sure the tip is visible, like on the dresser or next to the bathroom sink. Avoid leaving your housekeeping tips on the bed or nightstand, as these areas risk your cash getting jostled around or lost when bed sheets are changed.