I spoke with Birsen Hanim - the Director of SGK Fethiye - this morning and she was really friendly and helpful.
This is what she said about the subject:
Q: Who need to register at the SGK office?
A: All foreigners with a residence permit who have stayed longer than one year.
Q: If somebody has a one year residence permit and is at the moment for example in its four month?
A: No, they don't need to register since they haven't stayed longer than one year yet.
Q: If somebody has a six month residence permit but had a one year residence permit before that?
A: They won't need to register since we don't look at previous residence permits.
Q: Do you take in consideration the amount of time that people are actually staying in Turkey?
A (after having called the head office): No, we won't be checking passports to see how long they are actually staying. Anybody with a residence permit that has stayed longer than one year, needs to register.
Q: What happens if people don't register:
A: If they don't register before January 31st, they will be fined (note: I didn't have pen and paper with me and can't recall the exact figure but it was around 800 TL).
Q: What happens to foreigners who are currently not in Turkey and won't be able to come before January 31st?
A: Nothing has been said about that officially but I assume that there won't be any problems as long as they register after their return to Turkey and when they show the stamps in their passport.
Q: What if foreigners can proof that they have a health insurance in their home country?
A: They need to show an official translation of their social security status and it has to show that they will be covered in Turkey.
Q: How about foreigners with a private Turkish health insurance?
A: They still need to register and have a SGK insurance.
Q: What will the SGK insurance cover?
A: It will have the same coverage as it has for Turkish people but pre existing illnesses won't be covered.
Q: What is needed for registration?
A: Passport, residence permit and an official translation of marriage certificate for married couples. We also need an official translation of the Social Securiy status in their home country but since it is not realistic to expect that in such a short period of time, this can be brought later.
During the conversation, Birsen Hanim more or less contradicted herself.
I didn't point this out (since first of all it would be rude but secondly since I didn't want to point out the loopholes).
She said that foreigners with a one year residency permit need to register after they have stayed one year. But if the year isn't over yet, they don't need to register.
To me this sounds that nobody with a one year residency permit needs to register since you will always be within that one year (and they don't look at previous years).
It becomes a different story for people with residency permits longer than one year.
If you have an e.g. 3 year residency permit and more than one year has passed, you need to register.
I think this was more or less the whole conversation we had. If I think of anything else, I'll add it here.