Who must file
Anyone with global income for the year — business profits, employment, interest, dividends, pension or other income. A sole trader files even at a loss. An employee with a single salary whose employer completed the February year-end settlement does not. Companies file corporate tax instead.
Tax year and deadline
The tax year is the calendar year, and the return is filed and paid between 1 May and 31 May of the following year. A business large enough to fall under 성실신고확인, which must attach a tax agent's confirmation report, has until 30 June. Heirs file by the last day of the sixth month after the month of death; someone leaving the country for good files by the day before departure.
Filing step by step
- Wait for the NTS 신고안내. It says which income types NTS already has on you and which bookkeeping or estimated-expense method it expects.
- Log in to Hometax in May and open 종합소득세 신고.
- Work through the pre-filled figures. Your VAT returns, electronic tax invoices, card and cash-receipt sales and withholding records are already there; check them against your own books rather than accepting them.
- Claim deductions and credits, and answer the 성실신고확인 question. If it applies you have until 30 June, and the confirmation report must be attached.
- Pay by the deadline. Local income tax is filed and paid separately to your municipality through Wetax, not with this return.
Penalties for filing or paying late
Not filing the comprehensive income tax return by the 31 May deadline costs 20% of the tax that should have been reported. Filing but under-reporting costs 10% of the shortfall. Late payment adds interest-type charge of 2.2 per 10,000 of the unpaid tax for each day from the day after the due date until payment. A business that must keep books and fails to keep or complete them pays a further 20% of the tax attributable to the unrecorded income, with small businesses excluded. When non-filing, under-reporting and bookkeeping penalties overlap, only the largest of them applies.