Not jail but you'll get fined with a back-payment. They even tried to ask me where I was insured the last 15 years when I came back to Germany and where I worked and what not. I replied with none of your business and if you want to know if I paid social security in Spain send a request over the EU network to Spanish SS.

I should apply for social (Bürgergeld) and let the state pay the insurance. Quite frankly, in August I've been here for two years and so far NONE of my health issues have been properly addressed. Not the back, not skin issue, and certainly not dental work.