Determining the tax residency of individuals is an essential aspect, as it establishes the country in which they must pay taxes on their income and assets. In the Spanish case, if a person is considered a tax resident, they are required to pay tax on their entire worldwide income and their global net assets, regardless of where their assets are located. In contrast, those who do not have resident status will only pay tax on income and assets located in Spanish territory.

This tax difference has led to an increase in fictitious transfers of residence -also known as relocations- to jurisdictions with lower tax burdens. Faced with this situation, the Spanish Tax Administration has made it a priority to strengthen its control over false non-residents, using Big Data as one of its most relevant tools.

The Context: The Problem of Tax Residency in Spain

Article 9 of Law 35/2006 on Personal Income Tax establishes three main criteria – the existence of only one of them being sufficient- to determine tax residency in Spain:

1. Permanence Criterion (presential factor): Remaining in Spanish territory for more than 183 days during the calendar year. For calculation purposes, sporadic absences are also considered, unless the taxpayer proves tax residency in another country through a certificate issued by the corresponding tax authority.
2. Centre of Economic Interests Criterion (economic factor): The main core or base of the taxpayer’s economic activities or interests must be located in Spain, either directly or indirectly. This criterion considers factors such as the location of assets or significant income, and can determine tax residency even if the person has not resided in Spain for any day of the year.
3. Iuris tantum presumption Criterion (family factor): It is presumed, unless proven otherwise, that a person is a tax resident in Spain when the person’s spouse, not legally separated, and any minor children dependent on the person habitually reside in the country. This presumption can be rebutted by providing sufficient evidence, including a tax residency certificate issued by another state.

Due to the free movement of persons, proving actual residence in a territory is becoming increasingly difficult. Therefore, the Tax Administration has intensified its verification mechanisms, particularly using automated data analysis (Big Data) to detect potential fraud related to tax residency.

Big Data and The Transformation of Tax Surveillance in Spain

The Spanish Tax Administration uses Big Data as a tool to transform large volumes of data into useful information. Thanks to massive and automated data processing, the Administration can gather a greater number of clues that allow it to determine whether the necessary circumstances exist to consider a person a tax resident in Spain.

The use of Big Data in this area focuses on the systematic and automated collection of information, which facilitates a comprehensive analysis aimed at detecting physical presence in Spanish territory, the location of economic interests, and the existence of family ties -that is, the three determining criteria for tax residency according to Spanish regulations, which we have previously analysed.

Big Data-Based Digital Tracking Techniques Used by The Spanish Tax Administration

The Big Data tools used for tax residency monitoring include obtaining information from new sources, including:

1. Mobile phone geolocation: Geolocation allows us to determine a person’s location at a specific time through records of the device’s connection to telephone antennas, as well as through GPS data (e.g., Google Maps). Analysis of call history and roaming usage also helps confirm the taxpayer’s location. The Tax Administration has even used movement tracking at repeaters located in border areas -such as those of Portugal and Andorra- to detect potential violations.
2. Social media and the internet: Platforms such as Instagram, TikTok, X, or Facebook, as well as Google reviews, are a relevant source of information. By analysing posts, location tags, and interactions, the Administration obtains clues about the taxpayer’s actual activity. This digital footprint, voluntarily shared by users, can reveal signs of presence in Spain, economic activity, or external signs of undeclared wealth.
3. Automated web page crawling (Web Crawling): The Administration uses computer programs known as web crawlers or web spiders to explore freely accessible websites methodically and automatically. This technology allows information to be obtained on economic activities, property rentals, or the success of certain e-commerce sites. In this context, the crawling of more than 200,000 domains is planned to incorporate the data obtained into tax information databases.
4. Financial transactions and utility consumption:

• Bank transactions and card payments: The analysis of transfers, payments, and the location of card transactions allows for the reconstruction of spending habits, reflecting a taxpayer’s lifestyle.
• Household utility consumption: The levels of electricity, water, gas, and telephone bills associated with a property provide clues about its actual usage and, therefore, the length of time it remains in the area.

5. Other sources of information: The government also uses data from traffic fines—such as the location and vehicle registration—as well as information on medical records, health appointments, and use of social security or private insurance.

Tax Residency Control in Practice: The Shakira Case

A prominent example of the exhaustive application of Big Data-based tools to monitor tax residency is that of Colombian singer Shakira, who was being investigated by the Spanish Tax Administration. The tax inspector in charge of the case meticulously reconstructed the artist’s daily routine in Barcelona to demonstrate that her actual residence was not in the Bahamas, as she claimed, but in Spain, the country in which she should have paid taxes.

The Prosecutor’s Office argued that the artist had spent more than 183 days in Spanish territory -the legal threshold for tax residency- over several years: 246 days in 2012, 210 in 2013, and 243 in 2014. Although Shakira travelled internationally on numerous occasions, the inspector concluded that Barcelona was her “base camp” and described her absences as merely “sporadic.”

To support the €14.5 million fraud charge (corresponding to 2012, 2013, and 2014), the Treasury Department compiled a wide range of evidence, including:

• Personal monitoring: The artist’s presence at clinics, recording studios, beauty salons, and various businesses was verified. Her client’s record at a beauty salon was obtained, as well as records of visits to a private clinic.
• Financial transactions: Her credit card expenses were analysed. The singer’s team -her brother and three assistants- spent €418,046 at 279 establishments in Barcelona over a four-year period, including payments at restaurants, pharmacies, taxis, and hotels. Many of these expenses were paid with American Express cards used by her assistants.
• Social Media: Posts on various platforms were tracked, including content uploaded by fan clubs (third parties), which repeatedly placed the artist in Spain and were used as evidence of her regular presence in the country.
• Family and Personal Ties: It was established that her closest circle -family, stylists, producers, assistants, and friends- visited her in Barcelona. Furthermore, the school where her children attended reported that Shakira frequently visited them. Even her hairdresser confirmed that he saw her at her home in Esplugues (a town close to Barcelona) twice a week.
• Fictitious Residence: The defence maintained that the singer resided in Nassau, providing a permanent residence permit granted in 2007. However, the inspector proved that such a certificate could be obtained simply by purchasing a property. Furthermore, it was established that the utilities for the Bahamas home were paid for by a company and used by employees, and that an ex-boyfriend stated that Shakira had removed her belongings from the property. Based on all of this, the Administration concluded that the residence was used purely for “tax purposes.”

The Dispute between Efficiency and Rights

The application of Big Data techniques has increased the effectiveness and efficiency of the Tax Administration in the fight against tax fraud. However, their use must always be carried out within the constitutional and legal framework, as these practices can significantly infringe on citizens’ fundamental rights. Among the rights that may be affected are the right to the presumption of innocence -since the Administration must ensure that the evidence obtained is solid (there must be multiple indications), given that, for example, certain banking transactions could have been carried out by tax managers and not by the taxpayer under investigation-, the right to privacy -which requires that the data collected be truly relevant for tax purposes-, and the right to the protection of personal data -which requires compliance with the legitimizing requirements of Article 6 of the GDPR when collecting taxpayer information.

Given this intensification of control mechanisms, taxpayers are advised to retain as much documentation as possible in order to be able to refute, where appropriate, the conclusions drawn by the Tax Administration from Big Data. Ultimately, the Administration’s ultimate goal must be to maintain an appropriate balance between the fight against tax fraud and the protection of individual rights and citizens’ privacy.

Suggested citation:

Daniel Blanco Núñez , ‘Tax Residency and Digital Footprint: How Spain Uses Big Data to Detect False Non-Residents’ (Comparative Digital Law Blog, 17 November 2025) <https://lawandtech.ie/tax-residency-and-digital-footprint-how-spain-uses-big-data-to-detect-false-non-residents>.

About the author:

Daniel Blanco Núñez is a PhD student in ​​Financial and Tax Law at the University of León (Spain). He has completed both the Degree in Business Administration and Management and the Degree in Law separately at the University of León. Subsequently, he completed the Master’s Degree in Law also at the University of León. Daniel is a graduate of the European Masters in Law, Data and Artificial Intelligence.