The National Tax Service said Thursday that it would launch a large-scale investigation into offshore bank accounts with lump-sum deposits this year.

“The agency’s crackdown on tax evasion using tax havens abroad has seen some achievements in the first half of the year,” said an NTS official.

“In the second half, we will step up efforts to probe further into people who have deposited more than 1 billion won ($946,000) in overseas bank accounts.”

Some people used to hide illegal funds in-country in the past. Since the adoption of the real-name financial system, however, cases of overseas tax dodging have become more prevalent.

The tax agency has already launched a preliminary investigation into the lump-sum bank account owners who did not voluntarily report the origin of the money during the official period last month.

Many of them may have stashed illegal funds abroad, the agency thinks.

Under the current law, people who fail to prove the origin of undeclared deposits are to face fines of up to 5 percent of the amount and other penalties.

The fine is expected to increase to 10 percent of the undeclared money from next year and 45 percent from 2016.

“Even though the analysis of the voluntary reporting cases is still underway, we think the number makes up only 5 percent of the total cases suspected,” said the official.

Considering that many people do not recognize the voluntary reporting period, the NTS was also looking to exempt some part of the fines for voluntary reports.

By Lee Ji-yoon (jylee@heraldcorp.com)