To be left off without penalty or punishment thanks to one's own luck or to other people's indulgence

He's always up to no good, but he's mama's boy and he gets off scot-free every single time

Ne combina sempre una, ma è il cocco di mamma e la fa franca tutte le volte

I managed to buy a new vase before mother could even notice the old one was broken: I guess I'm home free

Sono riuscita a comperare un vaso nuovo prima che la mamma si accorgesse che avevo rotto il vecchio: l'ho fatta franca anche questa volta

This expression has nothing to do with Scotland, but rather with the early meaning of Scot (1500s), that is, a tax assessment. Thus, scot-free meant not having to pay such a tax