Across Mallorca, thousands of ads reuse the same license number. In many cases, this is not a technical detail: it is duplication, error or misuse of a legitimate license.

If a license appears on several ads, the problem stops being isolated and affects traceability, compliance and trust.

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What this means in practice

This problem has different consequences depending on who you are:

• Owners: your license number may appear on another host’s ad without your consent
• Agencies: duplicate ads for the same license can create operational conflicts and duplicated exposure
• Public administration: many properties per license make it harder to prioritise inspections and traceability
• Neighbours: several ads for the same home can inflate perceived supply on a street or in a building

The scope of the problem already shows in the data.

This is where the problem starts.

What is happening

Airbnb allows only one active listing per bookable home. When two or more listings reuse the same registry license for the same home, this directly breaks Airbnb rules for whole-home rentals, even if the license is genuine.

This is not only a data anomaly: in many cases it is a direct breach of the platform’s own rules.

Reuse can also happen without authorisation: another host or address uses your license number on their ad.

For the owner, this can mean a loss of control. For the neighbour, more apparent supply than really exists. For the administration, more difficulty inspecting.

Why it matters

When the same license is attached to many ads, inspection and traceability are harder and neighbours may see multiple listings for what is effectively one property.

Each duplicated license appears in 2.8 distinct listings on average: enough to show the issue is structural.

Whether a license appears on 2, 3 or 10 ads is not a nuance: it completely changes how you read the market.

34.9% of active listings are flagged as duplicate license. It includes some legitimate multi-unit establishment cases, but most correspond to single-home listings where sharing a license is not allowed.

This signal is part of a much larger economic problem. The full context is in the irregular revenue in Mallorca analysis.

Listings per duplicated license (distribution)

Tail: larger groups

These two measures show how much of the problem is concentrated in the largest groups (five or more ads sharing one license, and ten or more).

Distribution of listings by duplicated license

Quick read

• 41.8% of listings in duplicate groups are in groups of 2
• 23.5% are already in groups of 5 or more
• 3.3% are in groups of 10 or more

Each row shows how many listings share one license with that number of ads.

Average: 2.8 listings per license. But the average hides the extremes.

How we use this signal in RadarLicencias

Duplicate licenses are one of the signals we use to detect possible irregularities in Mallorca.

Check whether a license is duplicated →

It also helps explain why these old licenses remain so valuable: the flow of new grants has almost stopped, as shown in the licenses by year analysis.