Almost always from one of eight causes. Most are settings you or your channel manager control. A few are Booking.com's own programmes, and one is a rate that left through a door you forgot was open.
This guide takes them in the order worth checking: cheapest to rule out first. For each one, how to confirm it and how to fix it.
Before anything: is it really cheaper?
Two of the eight causes aren't undercuts at all. They're two different things being compared. Rule them out first, because they take five minutes and they explain a surprising share of screenshots.
Then note exactly what you saw: the date, the number of guests, the room, the board, the cancellation terms, the price, the currency, and whether you were signed in to Booking.com. You'll need all of it below.
The eight causes at a glance
| Cause | How to confirm | How to fix |
|---|---|---|
| 1. Not like for like | Match room, board, cancellation, guests and dates on both sides | Compare the same stay; offer your own non-refundable rate if you sell one there |
| 2. Tax or currency display | Look for "excluding taxes", a separate city fee, or a converted currency | Compare the final total in the same currency |
| 3. Genius and member discounts | Compare signed out with signed in | Decide whether you want the discount you fund; give your direct guests a members' price too |
| 4. Mobile and country rates | Check in the Booking.com app and from another country | Switch the targeted rates off, or offer the same on your site |
| 5. Booking Sponsored Benefit (BSB) | Your extranet shows the full rate, the guest sees less; check the BSB data in the extranet | Booking.com pays for it; ask how it applies to your listing |
| 6. A forgotten promotion | Look through active promotions and discounts in the extranet | End it, or match it on your own site |
| 7. Wholesale or bedbank leakage | A rate you didn't load, often room-only or oddly named | Find which contract it came from; tighten or end it |
| 8. Booking.basic | A non-refundable third-party rate on your listing (reported in 2019; we couldn't confirm it still runs) | Ask Booking.com; trace the wholesaler as in 7 |
1. It isn't like for like
What it looks like
Booking.com's cheapest room is non-refundable and room only. Your site's first price is flexible with breakfast. Both are "the price", and the gap between them can be large.
The same happens with room types (your cheapest room may not be sold on Booking.com at all), with guest count (a price for one guest against a price for two), and with length of stay (a one-night price against a seven-night average).
How to confirm it
Line up one stay on both sides: same dates, same guests, same room, same board, same cancellation terms. Only then compare. If the gap disappears, there was no undercut.
How to fix it
There's nothing to fix on the channel. If you sell a non-refundable rate on Booking.com, check that the same rate exists on your own site, at the same price or lower. Otherwise a guest comparing cheapest against cheapest will always find Booking.com lower.
2. Tax or currency display
What it looks like
Booking.com may show a price before some taxes or fees, with a note in small print that they are extra. Your site may show everything in one total. In Greece, for example, a per-night charge such as the climate resilience fee may be listed on its own; we couldn't confirm how Booking.com shows it today, so look at the price breakdown.
Currency does the same. A guest browsing in pounds or dollars sees Booking.com's conversion, which won't match your site's euro price converted at today's rate.
How to confirm it
Go to the final step before payment on both sides and compare the totals, in the same currency. Open Booking.com set to euros, not to your browser's local currency.
How to fix it
Usually nothing on Booking.com. On your own site, make it clear what the total includes, early in the booking flow, so a guest comparing isn't misled the other way.
3. Genius and member discounts
What it looks like
Genius prices are Booking.com's member discounts. When you join Genius, a 10% discount applies to your least expensive and most popular room type, and higher Genius levels can take 15% or 20%. You fund that discount, not Booking.com (Booking.com Partner Hub (opens in a new tab)).
For properties in APAC and EMEA, Booking.com says guests can also see the 10% Genius discount while signed out (Booking.com Partner Hub (opens in a new tab)). A signed-out check on your side may still not show every Genius price, and the guest who sent the screenshot may well have been signed in.
If you saw the price on Google rather than on Booking.com, click through and run the same two checks on the Booking.com page the link opens.
How to confirm it
Look at the same stay on Booking.com twice: once signed out in a private window, once signed in. If the lower price appears only signed in, it's a member discount. In the extranet, check which Genius levels you take part in and the discount each one gives.
How to fix it
This is a commercial choice, not an error. Genius brings visibility, and you pay for it in the discount. If you stay in, give your own direct guests something comparable: a members' price, a returning-guest rate, or a perk that a Booking.com booking doesn't get.
If you leave, the discount goes with it. In the European Economic Area, Booking.com says your prices elsewhere, your own site included, don't count toward Genius eligibility (Booking.com Partner Hub (opens in a new tab)). Weigh that against what the programme brings you, with your own booking data.
4. Mobile and country rates
What it looks like
A rate in your extranet may be aimed at guests on a phone or in the app, or at guests in particular countries. If one is switched on, you see your normal price on your laptop; a guest in another country, on a phone, sees less.
How to confirm it
Check the same stay in the Booking.com app, and on a mobile browser. For country rates, look at which markets you target in the extranet, or ask someone abroad to check for you. A VPN helps.
How to fix it
Switch the targeted rate off, or offer the same price to the same guests on your own site. If you target a market on purpose, that's a decision, but it should be one you know you made.
5. Booking Sponsored Benefit (BSB)
What it looks like
Your extranet shows your full rate, you loaded no promotion, and the guest still sees a lower price. With Booking Sponsored Benefit (BSB), Booking.com pays part of the room rate on the guest's behalf. You still receive the full transaction value, and pay your standard commission on the price you set (Booking.com Partner Hub (opens in a new tab)).
Because Booking.com funds it, it doesn't show up anywhere you set prices. Booking.com says a BSB price can also appear on metasearch in some regions, Google Hotel Ads included.
How to confirm it
Look at the BSB information in your extranet and at the details of recent reservations. The European Commission says hotels now have more performance data and reservation-level data on how BSB affects their bookings (European Commission, 28 September 2026 (opens in a new tab)). BSB is paid through Payments by Booking.com, so a property that doesn't use it shouldn't see BSB prices.
Until recently, a hotel's prices on other channels still counted toward BSB eligibility in the European Economic Area. On 28 September 2026 the Commission said Booking.com no longer looks at prices outside Booking.com when deciding it (European Commission, 28 September 2026 (opens in a new tab)). Our EU rate parity guide has the detail.
How to fix it
In the European Economic Area you can't opt in to BSB; Booking.com decides which bookings get it (Booking.com Partner Hub (opens in a new tab)). You're paid in full, so it doesn't cost you the booking's revenue. What it costs is that your own site looks dearer to that guest. Ask Booking.com, through your account manager, how BSB applies to your listing and what your options are, and keep the answer in writing.
6. A promotion you forgot
What it looks like
A last-minute deal from a slow week in spring is still running in September. Or an early-booker discount set to run "until further notice". Or two discounts that combine in a way you didn't expect.
How to confirm it
Open the promotions page in the Booking.com extranet and read every active one: its discount, its dates, and which rate plans it applies to. Do the same in your channel manager, which can push promotions and derived rates of its own.
How to fix it
End the promotions you don't want. For those you keep, offer at least the same price on your own site. A promotion shouldn't be the only place your best price lives.
7. Wholesale or bedbank leakage
What it looks like
You sell net rates to a tour operator or a wholesaler, meant to be packaged with a flight or sold only inside a closed channel. Some of that inventory is resold as a room on its own, at a price below yours.
It shows up most often among the smaller sellers on Google Hotels, but it can reach any channel that takes third-party supply. The giveaways: a room name that isn't one of yours, room-only when you never sell room-only, or terms you never loaded.
How to confirm it
Check whether the lower rate exists anywhere in your extranet or channel manager. If it doesn't, it came from outside. A test booking you make yourself, followed by which partner the reservation arrives through, is the most reliable way to trace it.
How to fix it
Find the contract. Check which partners receive net rates, what their contracts say about reselling them on their own, and whether the net rate is priced so it can't undercut you once a margin is added. Raise it with the partner, and end the allocation if it keeps happening.
8. Booking.basic
What it looks like
In 2019, hotel trade press described Booking.basic as a tier that appeared on some Booking.com listings when the rate the hotel gave Booking.com wasn't the cheapest online. Its rates were non-refundable and supplied by a third party, which the guest learned only after paying (Hotel Speak, January 2019 (opens in a new tab)).
That report is from 2019, and we couldn't confirm whether Booking.basic still runs, or where: we found no source from 2024 onwards that says either way. Treat it as a possibility to rule out, not a known cause.
How to confirm it
If a lower Booking.com rate on your listing doesn't match anything you loaded and isn't a Genius, mobile, country or sponsored price, ask Booking.com directly whether any third-party-sourced rates appear on your property.
How to fix it
Ask Booking.com whether you can opt out, and get the answer in writing. Then treat the source like cause 7: find which wholesaler the rate came from.
What changed in the EU
In the EU, Booking.com is a gatekeeper under the Digital Markets Act. Since 14 November 2024 it can't stop you selling at a different price anywhere else, your own site included (European Commission (opens in a new tab)).
So pricing lower on your own site is your call. The question that's left is whether it actually is lower, channel by channel, like for like, every night you sell. The rules, and what they don't cover, are in our EU rate parity guide. It's a summary, not legal advice.
Checking once is easy. Checking every night isn't.
Everything above works for one stay on one day. Prices move every day, and a promotion or a leaked rate can start on a Tuesday and run for a month before a guest mentions it.
That's what StayParity does. It reads the public prices on Booking.com, Expedia and every seller Google Hotels lists beside you, and puts each one next to your own site's price. It matches room, board, cancellation, tax basis and guests first, and a comparison it can't match that closely is labelled Cheapest rooms, so cause 1 and cause 2 don't pass for a like-for-like undercut. When a check finds Booking.com or Expedia undercutting you, and you've given us your listing there, it confirms it on that channel's own page.
What it doesn't do: it doesn't make test bookings. It tells you where and when you're undercut; this guide helps you find why.