Gangnam-gu proactively returns taxes paid twice by mistake

Gangnam-gu is reaching out to taxpayers who unknowingly paid their individual local income tax twice and have yet to receive a refund.

The district conducted a full review of 2,071 suspected double-payment cases from 2025 through August 2026, identifying 139 taxpayers eligible for refunds or canceled assessments totaling 167.75 million won ($125,000). It is also pursuing improvements to the filing system and payment process to prevent recurrences.

Individual local income tax is a self-assessed levy that taxpayers file and pay directly. It is divided into a comprehensive income component — covering earnings from business, employment, interest and dividends — and a capital gains component applied to income from the sale of assets such as real estate and shares. Despite the self-assessment structure, some taxpayers end up paying the same tax twice: they may file and pay before receiving a bill, then pay again when the bill arrives, or pay the bill first and then file again. When a tax agent handles the filing, the taxpayer may not immediately realize a double payment has occurred.

From January through September this year, district staff pulled records showing multiple payments in the same tax year from the tax system and cross-checked each against actual assessment records. The review covered 1,442 cases from 2025 and 629 cases from January through August this year, totaling 2,071. The district issued refunds or canceled assessments for 139 taxpayers — 112 in the comprehensive income category totaling 108.84 million won, and 27 in the capital gains category totaling 58.91 million won — for a combined 167.75 million won.

The district also analyzed the root causes of double payments. One of the most common is a delay in recording payments in the tax system. When some financial institutions or tax agents use paper payment slips, it can take more than a month for the payment to be entered into the system. In the interim, the tax may appear unpaid, triggering a new bill or prompting the taxpayer to pay again.

To address this, the district plans to petition the government to abolish paper payment slips. With electronic filing and payment now standard, the district argues that the paper-based method — slow to update and prone to error — should be eliminated to prevent duplicate payments. Scrapping the manual re-entry of paper receipts would also cut administrative costs.

While individual local income tax is in principle self-filed, the district office can calculate and issue a tax bill if a taxpayer's filing for a prior year is missing. The problem arises when a taxpayer, unaware of the district's action and seeing no filing record in the system, files and pays again — resulting in a double payment. To prevent this, the district plans to recommend a system change that would prompt taxpayers to check with the tax authority before filing a late return for a prior year when no filing record exists.

Going forward, Gangnam-gu will conduct a full review of suspected double-payment cases every six months. Staff training will also be strengthened to keep pace with increasingly complex tax records. The district intends to maintain a system in which the administration proactively identifies and returns overpayments, rather than waiting for taxpayers to spot errors and request refunds themselves.

"Proactively identifying and returning double payments that taxpayers were not even aware of is a concrete way to protect taxpayer rights," Gangnam-gu District Mayor Kim Hyun-ki said. "We will not stop at this one-time review but will pursue systemic reforms in parallel to build a tax administration that the public can trust."