Barcelona's Duplicate Image Problem: Why Bad Data in Public Databases Is Costing Residents Real Money and Time

A single apartment on Carrer de Provença appears three times in Barcelona's municipal property register. A hair salon on Passeig de Sant Joan is listed twice, under two different tax identification numbers, in the Ajuntament's commercial licensing database. These are not abstract data-quality footnotes. They are the reason a Gràcia family waited eleven weeks last year for a habitation certificate that should have taken three, and why a small business owner in Eixample received two separate municipal tax bills for the same premises before anyone caught the error.

The issue of duplicate image and record replacement — the systematic process of identifying, merging and correcting redundant entries in public digital databases — has moved from back-office IT concern to front-line civic problem. Barcelona's push to digitise its housing, commercial and urban-planning registries has accelerated since 2022, but faster data entry without rigorous deduplication protocols has compounded old clerical errors rather than erasing them.

How Duplicates Ripple Through Daily Life in Barcelona

The stakes are higher now because more decisions are automated. The Ajuntament de Barcelona uses its unified address database, linked to the national Cadastre, to cross-reference short-term rental licence applications, tourist tax compliance checks and social housing eligibility assessments. Mayor Jaume Collboni's administration expanded the tourist tax in April 2025, raising the overnight surcharge on cruise passengers to €7 and on hotel guests in peak season to as much as €4.25 per night. Revenue from that tax feeds directly into the city's affordable housing fund. When a property appears under two different cadastral references, the system can misfire — either billing the same owner twice or, more damagingly, failing to flag an unlicensed Airbnb-style rental at all.

The Institut Municipal d'Informàtica (IMI), the Ajuntament's technology arm based on Carrer de 60, in the Zona Franca, is the body responsible for data governance across city systems. IMI launched a deduplication audit programme in January 2026, targeting the Registre Municipal d'Habitatge first, because housing data feeds the most services. The registry covers roughly 780,000 residential units across the city's ten districts. Early internal findings, presented to the Consell Municipal's urban-planning committee in March 2026, identified duplicate or conflicting records affecting an estimated 4.3 percent of entries — a figure that translates to more than 33,000 addresses where at least one field contradicts another database source.

In practical terms, that 4.3 percent is not evenly distributed. Neighbourhoods with the oldest building stock and the most recent intensive renovation activity carry the heaviest duplication burden. Sant Pere, Santa Caterina i la Ribera and parts of Nou Barris, where social housing developments from the 1970s and 1980s were digitised from paper plans rather than fresh surveys, show the highest error density according to the March committee presentation.

What Residents and Small Businesses Can Do Now

The Oficina de l'Habitatge network — Barcelona operates seven such offices across the city, with the busiest at Carrer de Provença 339 in Eixample — has started offering a record-verification appointment specifically for residents whose licence or subsidy applications have stalled without clear explanation. Staff can request a live cross-check between the municipal housing register and the Cadastre reference in real time. The service is free and does not require prior appointment since June 2026, though walk-in queues at peak hours run to roughly 40 minutes.

For commercial operators dealing with duplicate tax references, the Agència Tributària de Catalunya maintains a correction request portal that accepts digital submissions with a cadastral certificate attached. Processing time is currently stated as 20 working days, though the backlog from the January 2026 audit referrals has pushed some cases past that window.

IMI has committed to completing the first phase of the housing registry deduplication by October 2026, ahead of the winter rental season when licence applications spike. A second phase, covering commercial premises and the city's tourism-activity register, is scheduled to begin in early 2027. Residents whose applications are caught in limbo in the meantime have one concrete option: request a written explanation of any processing delay under the Llei de Procediment Administratiu Comú, which obliges the Ajuntament to respond within ten working days. Knowing that the problem has a name — and a scheduled fix — is a start.