Registered mail describes letters, packets or other postal documents considered valuable and in need of a chain of custody that provides more control than regular mail. The posted item has its details recorded in a register to enable its location to be tracked, sometimes with added insurance to cover loss. Can be used for postcards, letters, and large envelopes.

In most countries, the use of registered mail require labels with a 13-digit reference number and corresponding barcode. The first two letters indicate registration (usually "RR") while the last 2 letters usually represent the country where the registered item was posted.
 
ES is the country code for España (Spain).

Registered mail can be tracked on Correos' website (www.correos.com) and the destination country's national postal service (UPU-recognized).

The label is free and fee will only be charged during registration time at the post office.

Signature is required upon delivery and must be delivered personally.