Spain - Social Security

In order to get a TIE as a UK citizen (but applicable to everyone who is not a EU citizen) you need a Spanish Social number.

Has anyone had experience of applying for one both as a younger working person and also as a retired person?

I am a British citizen with a UK passport and have accepted the 90 day rule (90 days in every 180) until now. However, I now want to spend more time in Spain and need to get an NIE
I receive a UK pension, but am still working as well

We paid an attorney to get us the Spanish NIEs. I had looked around for appointments at the police stations that issue them but found nothing available. The attorney explained that individuals/companies buy up the appointments so they can resell them. I can’t be sure that’s correct but the attorney received them in a few days so it a was fast and efficient process for us. I don’t think your age or work status matters. It matters what you are going to do like rent a flat.

Part 2: We have now been asked for our NIEs a number of times. Most recently to buy stuff at IKEA - which seems odd to me - and to sign up for a supermarket discount card.