Update March 2017. The letter is now being provided in English and Spanish for those enttiled to free healthcare under the ‘resident pre April 2012 law’ and other situations. Contact the:
NHS Overseas Healthcare Services
Telephone: +44 (0)191 218 1999
Monday to Friday, 8am to 6pm
Saturday, 9am to 3pm
Ignore the comments and updates below as these are now for our records only.
UPDATE 10/08/2016
The letter is no longer available from the Overseas Team. There is now a new system in place both for the application to be made from the INSS offices. We are in touch with the INSS healthcare head office and the HMRC in the UK. We will clarify as soon as we receive full information.
Update 15/11/2016
We have communicated with the relevant office in the UK and after many emails, the final answer from them below. We have also written to the head department of the INSS in Madrid with this information. We hope that they will provide the information to their individual INSS offices.
“In general, foreign social security authorities send us documents SO40 which in turn enables us to issue documents SO41 to them for individuals who have lived in the UK and gone abroad. Document SO41 assists a person in sickness benefit claims abroad”.

If any residents still have problems, please post on the Ask for Advice section of the website or email us.