A hospital is crowded with patients and their guardians seeking medical treatment in Seoul, Jan. 6. Yonhap

The National Health Insurance Service (NHIS) admitted to errors in statistics regarding foreign subscribers, Sunday, revealing that the health insurance deficit attributed to Chinese subscribers had been overstated by 120 billion won ($82 million).

According to a report submitted by the NHIS to Rep. Kim Mi-ae of the ruling People Power Party, the agency adjusted the financial balance for Chinese subscribers last month due to miscalculations in assessing insurance premiums for the past years.

In 2020, a manual calculation error led to an inaccurate report. Initially, the financial balance for Chinese subscribers that year recorded a 23.9 billion won deficit, but after correction, it was revised to a 36.5 billion won surplus.

A similar issue occurred in 2023, when a mistake in classifying country codes resulted in another major revision. The initial report showed a 64 billion won deficit for Chinese subscribers, but after correction, the figure was adjusted to a 2.7 billion won deficit.

These huge discrepancies are particularly critical, as China is the only country among the top 10 nations with the highest number of foreign subscribers that has consistently run a deficit in Korea's national health insurance fund.

Amid growing reports of some Chinese nationals registering as dependents of Korean citizens to receive health insurance benefits without paying premiums — sometimes leaving for China immediately after treatment — concerns about Chinese people "free-riding" on the system have intensified.

China's insurance balance in Korea previously recorded deficits of 98.7 billion won in 2019, 10.9 billion won in 2021, and 22.9 billion won in 2022.

"The NHIS's credibility as a public institution has plummeted, as even the most fundamental statistical data for legislation and policymaking is riddled with errors," Kim said.

The NHIS acknowledged that the errors "may have impacted trust in its statistics." But it added the financial balance of foreign subscribers by country is not a regularly produced statistic but is a calculated only when needed, such as upon request from the National Assembly. It said the corrections did not result in any financial loss to the fund.