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That Registration Number in the Listing Is Not Decoration

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A printed notice taped inside the entrance hall of an old apartment building

A printed notice taped inside the entrance hall of an old apartment building

New York City's Mayor's Office of Special Enforcement publishes every short-term rental registration it has granted, along with the listings attached to each one. Having built that dataset, it read it. As of early June 2025 the office estimated that roughly twenty per cent of registered listings were offering illegal occupancy, and it began sending warning notices to the hosts concerned. These were not rogue operators hiding from the city. They had applied, been approved, received a number, and then advertised something the number did not cover.

That is the first thing worth knowing about registration numbers. The number is not a seal of approval. It is a specific factual claim about a specific flat, issued by somebody other than the person selling you the stay, and the claim is narrower than most guests assume.

The second thing worth knowing is that the claim means six different things in six different places.

New York: the rule almost nobody reads

Local Law 18 of 2022 requires hosts to register with the Office of Special Enforcement and bars booking platforms from taking payment for a rental that holds no registration. Enforcement of the platform side began in September 2023, and platforms now run each listing through the city's verification system.

What the law did not do is change the underlying rules, and those are stricter than the registration requirement suggests. A host, owner or tenant alike, may not let a whole apartment or house to visitors for a stay shorter than 30 consecutive days. That applies to every permanent residential building regardless of size. A short stay is lawful only where the host is living in that same unit alongside the guests, where the paying guests number two at most, and where host and guests maintain a common household. The city adds a set of physical conditions, and they are fire rules wearing a housing hat. The enforcement office permits those two paying guests only if every one of them has, in its words, "free and unobstructed access to every room and each exit within the apartment", and it warns that internal doors cannot carry key locks that let a guest shut a room behind them, because a locked internal door is something to get past while the hallway fills with smoke. Nobody may sleep in an attic, cellar or garage.

So a New York listing that displays a registration number and offers you the whole apartment to yourself is making two statements that cannot both be true. The registration office will not approve an application for a stay with no host on the premises, for a whole unit, or for more guests than the law's limit of two. Rent-regulated and public housing units cannot be registered at all, and building owners can put their addresses on a prohibited buildings list. Stays of 30 consecutive days or more sit outside the scheme entirely, as do units in Class B multiple dwellings, which are legally approved for short occupancies in the first place.

A small plaque fixed beside a residential doorway in Japan next to an intercom and mailbox

Barcelona: a number that should be on the wall

A legal tourist flat in Barcelona holds a licence from the city and a Catalan Tourism Register number. The city's own guidance is explicit about where that number is supposed to appear: a sign showing it must be displayed inside the property, and the number must be given to visitors when they make their booking. Guests in a legal flat are also given a 24-hour telephone number to call if something goes wrong during the stay.

Those two details are the practical test. If the number never arrived with your confirmation, and there is no sign inside the flat, the paperwork is not merely untidy.

Barcelona has also decided how this ends. Faced with its housing situation, the council has resolved to withdraw all holiday-let licences in the city by 2028, a move it expects to return around 10,000 homes to residential use. It is running complaint channels and support measures for residents in the meantime. A licensed flat in Barcelona is a wasting asset, and some operators are behaving accordingly.

Lisbon: the number is the permission

Portugal's Alojamento Local scheme works by prior notification through the electronic single counter. The application is given a registration number if the competent câmara municipal does not object within 60 working days, or 90 working days where the flat sits in a designated containment area. The document carrying that number is the thing that legally permits the establishment to open to the public and to be advertised at all.

Turismo de Portugal states the consequence plainly: offering, making available, advertising or brokering an unregistered local accommodation establishment, or one whose registration is out of date, is not permitted, and electronic platforms that list accommodation must require and display the RNAL number. The register is public and searchable by name, address or municipality, and the data in it is validated and transmitted by the municipality itself.

There is a quieter clause that matters more to a guest than any of this. The registration stays valid only while the operator files proof of a civil liability insurance policy, on receiving the number and again whenever the policy is renewed or changed. An unregistered flat has not filed one. If you fall down an unlit staircase in it, there is nothing behind the host.

A steep narrow stairwell inside an Amsterdam canal house with a suitcase left partway up

Amsterdam: registration, permit, and a report for every stay

Dutch national law sets the frame. The Housing Act 2014 allows a council to require a registration number for tourist letting, makes it an offence to offer a home for tourist letting without quoting that number in every advertisement, and separately forbids a digital platform from publishing such an offer without it. Councils may cap the number of nights per year and may impose a notification duty for each individual letting. And once the council has notified the platform that a particular home has already used up its allowance of nights for the year, it can forbid the platform from showing that listing for the rest of the year. The trigger is the flat's exhausted counter, not any finding against the person letting it.

Amsterdam uses all of it. A permit is required, and every booking must be reported in advance through the national tourist rental registration system, with arrival and departure dates. The host receives a confirmation number and, according to the city's own instructions to hosts, an immediate readout of how many nights they have used and how many remain.

The cap is 30 nights per permit per year, which the city's own policy document describes as the lowest figure anywhere in Europe. That document also sets out an escalation ladder: where a neighbourhood crosses thresholds for nuisance and tourism pressure, the cap drops to 15 nights, and the final rung is a temporary halt imposed in principle for three years. The first rung has already been climbed. A designation order in force since 1 April 2026 cuts the cap to 15 nights in eight neighbourhoods, which it names as "Burgwallen-Nieuwe Zijde, De Weteringschans, Grachtengordel-West, Grachtengordel-Zuid, Haarlemmerbuurt, Jordaan, Nieuwmarkt/Lastage en Oude Pijp", the first seven of them central and the last one in Zuid. Measures are announced at least three months ahead so that existing bookings can be moved.

A host who has run out of nights has two options. One of them is to cancel on you.

Paris: two permissions, not one

France separates things that guests routinely conflate. There is the declaration to the mairie, and there is the authorisation for change of use under the construction and housing code, which is what turns a dwelling into a furnished tourist let in the eyes of the law.

Registration used to be a local option, switched on commune by commune, and for years that was the single most confusing thing about the French system. It is no longer optional. The loi Le Meur of 19 November 2024 extends declaration with registration to the whole country, a decree of 19 March 2026 built the national teleservice that issues the numbers, and the environment ministry's own guidance describes the procedure as being generalised across the national territory from May 2026, timed to the European regulation that now sits over all of it. The number runs to 13 characters in three groups. It must appear on the advertisement, on a platform listing as much as anywhere else, alongside a line saying whether the seller is a private individual or a professional. An intermediary has to ask the host for a signed statement that the prior formalities were done before it will publish at all.

The day limit moved with it. A principal residence let to tourists is capped by its commune at somewhere between 90 and 120 days a calendar year, so the familiar 120 is now a ceiling on the local rule rather than the rule itself. Overshooting it is a civil fine of up to 15,000 euros per flat. The change-of-use rules are where the serious money sits: converting without authorisation risks a fine of up to 100,000 euros, an order to put the flat back as it was, and a penalty of up to 1,000 euros per day for every square metre until that happens.

Then there is the trap that no registry will show you. A building's co-ownership rules may include a clause restricting the premises to residential use, which bars any professional activity including tourist letting, and owners in general meeting can vote to prohibit tourist lets outright. A flat can be correctly declared to the town hall and still be forbidden by its own building. That argument is usually had in the stairwell, during somebody's holiday.

A hand holding a phone in front of a Barcelona apartment facade with wrought-iron balconies

Japan: look for the sign

Japan runs two main routes. An operator can hold a licence under the Inns and Hotels Act, or file a notification under the Private Lodging Business Act, in which case the property may be used for lodging no more than 180 days a year, counted from noon on 1 April to noon on 1 April.

The notified operator carries a list of duties that are, in effect, a description of what an illegal minpaku is not doing. A sign must go up somewhere the public can see it, at every notified property. A lodgers' register must be kept, recording nationality and passport number for any guest without a fixed address in Japan. Guests who are foreign tourists must be told, in a foreign language, how the appliances work, how to get about, and what number to dial in a fire or other disaster. Guest numbers, nights and a breakdown by nationality are reported to the prefectural governor six times a year. If the property has more than five lodging rooms, or if the operator will be absent while guests are staying, management must be entrusted to a registered administrator.

The sign is the check, and it takes four seconds. A property operating quietly with no sign anywhere near the entrance has not notified anybody.

The layer that now sits above all of them

Since 20 May 2026, the date the text itself sets for its own application, Regulation (EU) 2024/1028 has applied across the Union. Platforms must design their interfaces so that a host supplies a registration number before a listing can go live in an area where a registration procedure exists, must display that number clearly as part of the listing, and must make reasonable efforts to check the validity of those numbers at random and on a regular basis through national single digital entry points. Where a host has supplied false or invalid information, the competent authority can withdraw the registration number and order the platform to remove the listing without undue delay.

Spain tried to build the domestic plumbing for this and had it taken apart. Real Decreto 1312/2024 created a single national rental registration number, issued through the property register, without which a unit could not be offered on an online platform at all. On 21 May 2026 the Tribunal Supremo, hearing a challenge from the Generalitat Valenciana, annulled the provisions that created that register. The state, it held, had no competential title for a national register laid over the regional ones that already record tourist properties. What survived the judgment is the digital single window and the duty on platforms to transmit data. So the number a Spanish listing should carry is a regional one, which in Catalonia is the tourism register number the Barcelona section has already described. Amsterdam's policy document notes the practical effect from the city's side: from May 2026 it gets platform data on overnight stays per address.

The blunt consequence for a guest is new. A listing can now be removed between the moment you book and the night you arrive, by order of an authority that has never heard of you.

What this costs you when it goes wrong

Cancellation at short notice in a city that is full. No insurance policy behind the property. No 24-hour number when the boiler fails. Sleeping arrangements in a cellar that a certificate of occupancy never approved, with a fire exit somebody has blocked with a wardrobe. Neighbours with a complaints form, an escalation ladder and, in Barcelona's case, a council actively soliciting reports. And no standing in the proceedings when it unravels, because a short booking is not a tenancy and you are not a party to any of the arguments that produced it.

Barcelona is the exception that proves the point, and it is worth reading closely. If a flat is sealed while tourists happen to be in it, the council undertakes to rehouse them at no cost and to bill the owner for it. That is a decent outcome and it is not a right you hold. You appear in the file as an expense to be recovered, not as a party to anything.

Against that, the check costs two minutes. Portugal's register is public and searchable. Barcelona's council page will take an address and tell you whether a licensed flat is at it. New York publishes its registrations, their statuses and their associated listings precisely so that guests can look up a listing before booking it. Every one of these systems was built on the assumption that somebody would actually use it.

Everything else in a listing is written by the person taking your money. The photographs are chosen, the description is marketing, the reviews are a system with known weaknesses. The registration number is the only line in the whole advertisement that was issued by someone else and can be verified against a source that has no interest in the sale. Copy it. Paste it. If the flat is not there, the listing has already told you what you needed to know.

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