While reading this article I was wondering, do tax offices have access to PNR flight data (international flights to/out of EU)? Looks like it is used only by law enforcement in case of preventing/analyzing/prosecution terrorist offences and serious crime. This data is available for 6 months, after that it has to be anonymized and deleted after 5 years.
PNR EU directive
PNR EU directive
Directive - 2016/681 - EN - EUR-Lex
eur-lex.europa.eu