Have you had treatment recently at your local NHS hospital? If so you are likely to receive a letter from the hospital written in Spanish. This letter will tell you of the treatment received and cost. Do not be alarmed as in most cases and if you are under the Spanish health service, this is not a bill.
You should find in the body of the letter in bold, wording similar to this: ‘‘SUPONEN COSTE EN NINGÚN CASO TENDRÁ QUE ABONAR’ This is telling you that you do not have to pay.