What is a Denuncia, when would I make one and how would I do this ? ....
If you believe that you have been the victim of a crime in Spain or you believe that you have witnessed a crime, you are required to make a Denunica (or 'denouncement' in English), which is basically a formal statement made to the police. you are able to do this at any office of the Policia Local or Guardia Civil. It is better to make this statement in person, but if your level of spoken Spanish is not competent then you should take somebody with you to translate on your behalf. You should also take with you your NIE and passport, and any other documentation or evidence that may support your statement.
There is provision to make a denuncia by telephone if needs be - in English - and one can be made by calling 902-102-112 before you make the call you should have your NIE (or passport number) available, together with your address, for identification purposes.
It is likely that the first person to answer the phone may not speak or understand English so you should at the very least be able to ask to be transferred to an English speaking operator in Spanish.
The operator will then take you through a series of questions to determine the nature of the crime and take down a few basic questions to try and arrive at an understanding at what has occurred. It is recommended that you go through the sequence of events in your mind beforehand so you can be clear on this, making notes if necessary. Once all the information has been taken down you should be given a reference number – you have now made a denunica. The operator will then enter the details of your statement into the system and the denuncia report will be despatched to your nearest police station. You should confirm where exactly this is, as you will be required to report there with your documents, and quoting the reference number that you have been given, within 48 hours.
If you believe that you have been the victim of a theft or crime that is likely to result in a claim with your insurance provider, you will be required to present a copy of this, similar to a crime report in the uk, so it is always a good idea to take multiple copies of this.
Once your statement has been filed, the police force in question is obliged to investigate to find out if a crime has actually taken place, and if so the nature of the crime, together with the identity of the person(s) committing the crime and their guilt. Once this investigation has been completed the details may be passed over to a public prosecutor who will decide whether to proceed with any legal case or not, and if so, in what manner.