Large South Korean companies have sent more than $400 billion to offshore tax havens over the past eight years, with nearly 40 percent of the amount yet to be returned home, data showed Sunday.

According to the data by the Bank of Korea and other government agencies, local big firms remitted a combined $432.4 billion to tax havens abroad between 2007 and 2014.

Of the total, $158.3 billion has been repatriated so far, with the rest, or 37 percent, yet to be returned home.

Only $12.3 billion was classified as investment money, with the net inflow of large firms' funds into offshore tax havens soaring 112 percent on-year to $24.4 billion in 2014.

There have been growing suspicions that some of the money has been sent to tax havens to avoid taxes or to be used for creating secret funds.

During the same period, local small and medium enterprises sent a total of $172.2 billion to offshore tax havens, while they repatriated $253.9 billion, according to the data.

The National Tax Service has designated as tax havens 50 nations, including the Cayman Islands, the British Virgin Islands, Singapore and Switzerland.

The tax authorities have been stepping up efforts to tackle tax evasion using overseas tax havens. In 2013, the NTS collected 1.08 trillion won ($920 million) in penalties from those tax evaders, up from 825.8 trillion won a year earlier. (Yonhap)