Korea Payroll & Tax API › early-repayment-fee

South Korea early loan repayment fee (jungdo sanghwan susuryo)

South Korea early loan repayment fee (jungdo sanghwan susuryo): repaid amount x fee rate x remaining days / fee period (usually 3 years, after which the fee is waived).

Price: $0.01 USDC per call over REST (x402 on Base, no API key). MCP: free as early_repayment_fee at https://api.kkuldogu.com/mcp. Basis year: 2026.

Input

Field	Type	Required	Description
`repayAmount`	number	yes	Amount repaid early (KRW)
`feeRatePct`	number	yes	Fee rate in percent from the loan contract, e.g. 1.2
`elapsedDays`	number	yes	Days since the loan was taken out
`feePeriodDays`	integer		Period during which the fee applies, in days; default 1095 (3 years)

Example request

curl -X POST https://api.kkuldogu.com/v1/early-repayment-fee -H "content-type: application/json" \
  -d '{"repayAmount":100000000,"feeRatePct":1.2,"elapsedDays":365}'

Without payment this returns 402 with x402 payment requirements; an x402 client pays $0.01 USDC and retries.

Example response

{
  "basisYear": 2026,
  "currency": "KRW",
  "disclaimer": "For reference only, not legal, tax or financial advice. Computed from South Korean statutes and standard formulas as of 2026; reliefs, exemptions and special cases not shown in the result are not modeled, and rules may have changed. Confirm with the relevant office, court, lender or a professional before acting.",
  "source": "https://kkuldogu.com",
  "tool": "early-repayment-fee",
  "input": {
    "repayAmount": 100000000,
    "feeRatePct": 1.2,
    "elapsedDays": 365
  },
  "result": {
    "fee": 800000,
    "remainingDays": 730,
    "waived": false
  }
}

For reference only, not legal or tax advice. Uses official 2026 Korean rates and the same formulas as the kkuldogu.com calculators; actual payroll, NHIS/NPS notices and tax settlement can differ. · Calculators for people (Korean): kkuldogu.com · API home · llms.txt · OpenAPI