A protester holds a placard calling on the goverment to lower the inheritance tax, during a joint rally of multiple civic groups and labor unions in front of the presidential office in Seoul's Yongsan District, June 25. Yonhap

Seven out of 10 Koreans from middle-class households had troubles with inheritance, according to a report, as more taxpayers nationwide are becoming subject to an inheritance tax under outdated regulations.

Released by Hana Institute of Finance this week, the report summarized cases of middle-class individuals bequeathed inheritances from parents or other senior family members.

The middle class was categorized as households whose net wealth falls in the mid-50 percent range. That is equivalent to 500 million won ($360,000) for those who live in Seoul and the greater Seoul area and 300 million won for those in the rest of the country.

"And 70 percent of them struggled with lack of legal knowledge, lack of preparation of relevant documents as well as disputes with other inheritors within the family," the report read.

Correspondingly, eight in 10 middle-class individuals found "sufficient time and efforts in advance crucial to inheriting wealth without troubles."

Regarding the right timing to start the inheritance process, those in their 40s said "The earlier the better," while those in their 60s said when the person who wants to pass down their wealth gets sick frequently.

The report came as the value of homes in Seoul has risen sharply in the wake of a housing bubble.

In the meantime, inheritance tax rules remain unchanged for years, resulting in an increasing number of middle-class individuals being subject to the tax.