Visitors to Spain will face more paperwork from Monday when a new law requiring hotel owners and car hire firms to send personal information about their customers to the government comes into effect.
The rules, which also apply to rental properties and campsites, are being brought in for national security reasons, but tourism experts have raised privacy concerns and warned it could lead to delays at check-in desks.
The data required will include passport details, home addresses and methods of payment for those over the age of 14. It will be submitted to the Ministry of the Interior.
The Confederation of Spanish Hoteliers and Tourist Accommodation (CEHAT) said it was concerned at the impact on its members' businesses and was considering legal action to challenge the rules.
Spain is the second most-popular destination for tourists in Europe, with more than 82m visitors in 2023, led by 17m from the UK.
The start date of the new rules - officially known as Royal Decree 933/2021 - was pushed back from 1 October to 2 December, to give the industry more time to prepare.
Both tourists and Spanish residents will be required to provide information, which will also include phone numbers, email addresses and the number of travellers.
Businesses will need to be registered with the Ministry of the Interior, report the data collected daily and keep a digital record of the information for three years and face fines of between €100 and €30,000 (£80-£25,000) for breaches.
Meanwhile, Airbnb has told property owners renting out accommodation through its website they will need to be registered with the Spanish government and collect data from their customers.
In a statement, the Ministry of the Interior said the regulations were "justified for the general interest for the security of citizens against the threat of terrorism and other serious offences committed by criminal organisations".
But the hotel industry body CEHAT said the the change “puts the viability of the sector in serious danger”.
It said both tourists and Spanish citizens will have to deal with "complex and tedious administrative procedures, compromising their accommodation experience".
It added hoteliers were being are forced to comply with "confusing and disproportionate regulations" that go against other European directives related to data protection and payment systems.
Travel journalist Simon Calder told the BBC the Spanish government was concerned about organised crime and terrorism and "simply want to know... who's coming and going, where they are staying and what cars they are renting".
It is expected that many accommodation and car hire providers will automate the collection of data through online registration.
Mr Calder envisaged there would be "quite a lot of standing around at reception" when the rules kick in but said it was "very low season" at the moment and that would give businesses a chance to get used to the system.
Gibraltar-based Penelope Bielckus, travel content creator at The Flyaway Girl blog, said the new rules "add another layer of paperwork that can feel like a chore when all you want is to relax on holiday".
And she agreed they "might slow things down a bit, especially at check-in, since there’s now more paperwork to handle".
But she said while Spain's level of data collection "does feel stricter" than elsewhere, that hotels and car hire companies already collect much of the information required from travellers.
"We’re still waiting to see how this will affect things like last-minute hotel bookings or car hire," she added. "Hopefully, it won’t cause any major problems, but it’s definitely something to keep an eye on in case of any changes."