When countries actually bankrupt? (Fearless Blue)

Documentation says when country assets go over -10T negative but in my world these is 3 country empire who have one country -15T negative one country -13T and one -8T negative on country assests.

The United Kingdom of Sappa from FB world. He has been negative like this for months from last december 2010 (real time) and he is still not dropping from game.

Good question, I'm unsure of the threshold for bankruptcy now, slaves send there debt to the main if they are closed, but what the main closes at I know is far more than 10T debt. Probably closer to 100T nowadays.
If a player is inactive for a long time like your example his countries will eventually get reset to C3 status. Again dont know how long this takes but it is quite a while.
If you were thinking of taking over one of these countries, the max debt you would inherit would be 2T, the rest gets lost in the void.

I believe it is -60T$

Tnx I was thinking getting some inactive player countries but I dont want to inherit their 8T debt plus -30T negative money on my empire.

I believe if you conquer an inactive with more than $2T in debt or negative cash, you'll receive cash equal to (negative cash + loans - $2T) so that would cap the negative cash inherited to a very low amount.