Majorca in the Balearic Islands
Spy planes are flying over the the Balearic Islands to snare tax dodgersGetty Images

The Spanish Treasury has deployed spy planes over the Balearic Islands to catch tax cheats carrying out unregistered building work.

Mallorcan newspaper Ultima Hora reports that the Spanish government is flying light aircraft over the islands to take aerial photographs of properties where building work has been carried out and not declared. This includes additions that would increase the value of a property and therefore the amount of liable tax, such as extensions and swimming pools.

By not declaring such work, tax cheats have been able to dodge a higher Impuesto sobre Bienes Inmuebles (IBI) bill, a tax bill payable by all property owners in Spain based on the perceived value of the property in question.

Aerial surveys of 28 municipalities across the Balearic Islands between 2013 and 2015, including popular tourist destinations like Mallorca and Ibiza, found 21,652 properties that had been altered in some way without being declared, reported Ultima Hora.

Revenues from IBI goes toward local authorities to help them maintain local infrastructure and the general upkeep of the area. Aerial shots from spy planes are reported to have raised the average IBI bill across the monitored municipalities by €309 (£240, $350) since being deployed, which will pull in an additional €6m for local authorities.

Spain isn't the only country using controversial spy plane technology. Federal authorities in the United State are currently using light aircraft equipped with night vision and thermal imaging to carry out surveillance and snare drug and sex traffickers.