They are mostly people working in well-paying jobs -- lawyers, doctors, popular cram school teachers, owners of multiple homes and owners of large-scale restaurants and bars -- the agency said.  

The probe is part of the tax agency’s policy of intensifying its crackdown on tax evasion attempts by well-paid, high-status people. The plan involves keeping close tabs on tax evasion that could take place during wealth transfers and inheritance.

For the past five years, the NTS conducted a similar probe into 5,452 such people, leading to the collection of about 3.86 trillion won (US$3.40 billion) more in dues.

The tax agency said that it will toughen its crackdown on market-distorting activities, as well as loan sharks and others, that could hurt the livelihood of low-income citizens. Offshore tax evasion by businesses will be under heightened scrutiny this year, the NTS noted.

By Song Seung-hyun and newswires (ssh@heraldcorp.com)