This is a good one.
At the end of 2008 the Social Security here (hereinafter referred to as the SS) accidentally set up a second contributions account for Mrs. T42. In 2011 they realized that although we were submitting her annual declaration of earnings, no contributions were being paid into the spurious account. That they were landing in the correct account was invisible to them because (deep breath and prepare to boggle) the accounts were not referenced by her unambiguous SS number but by her name and Register of Commerce number, and since they had her down for two different types of professional activity these numbers were different. They had also used slightly different spellings of her name - one of them left out her middle name, the other had it hyphenated onto her first name.
In 2011 they sent us out of the blue a demand for 8000+ euros, with about 3 minutes grace to pay. I battled with them for months, with them gazumping the penalties every month or so, before they finally admitted their mistake and cancelled everything. Zero excuses, of course.
This January, three days after I had my stent put in, a letter arrived from the SS, saying that they were recalculating Mrs. T's contributions and we would presently receive (get this) a final demand. Yesterday, after almost a month of nail-biting, a bailiff's letter arrived: 3000+ euros to pay in the next 15 days or else.
I just got off the phone to the SS-Einsatzgruppe. "Oh. The stop code on the 2011 dossier was unset by accident. Forget about everything. Very sorry and all that."
One of the things they tell you to avoid after a heart problem is stress.