If you are found personally responsible for tax evasion >1e6€ then the minimal penalty is prison sentence without parole option. This is true for many EU countries including Italy. Idk. about the max. prison length in Italy for this but e.g. where I live in the EU you are likely looking at ~15 years for 1e9€ tax evasion.

The reason executives commonly avoid such penalties is because they avoid being found personally liable by claiming they didn't known, did misunderstood the situation, where deceived by others etc.

Through it should be noted that this case is a bit unusual and complicated. The tax dispute itself isn't as simple as Amazone directly having avoided paying their own taxes. And the case of missing taxes has already been settled. This new current investigations are criminal investigation (i.e. the failure of paying taxes is assumed to have been intentional instead of a booking error) and seem to be more targeting executives for having committed crimes (instead of targeting Amazone the company).

Or in other words, Italian prosecutors are feed up US companies not caring for EU law and no one being hold liable.

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(1): Without option to have it replaced with long time parole.