Korea Payroll & Tax API › deposit-interest
South Korea bank deposit or installment-savings interest after tax: maturity amount with simple or monthly-compounded interest and the 15.4% interest withholding tax (or 9.5% preferential, or tax-free).
Price: $0.01 USDC per call over REST (x402 on Base, no API key). MCP: free as deposit_interest at https://api.kkuldogu.com/mcp. Basis year: 2026.
| Field | Type | Required | Description |
|---|---|---|---|
kind | deposit | savings | deposit (lump sum) or savings (fixed monthly installment); default deposit | |
amount | number | yes | Principal, or monthly installment for savings (KRW) |
months | integer | yes | Term in months |
annualRatePct | number | yes | Annual interest rate in percent |
compounding | simple | monthly | simple (default) or monthly compounding | |
taxRate | 0.154 | 0.095 | 0 | Interest tax: 0.154 general (default), 0.095 preferential, 0 tax-free |
curl -X POST https://api.kkuldogu.com/v1/deposit-interest -H "content-type: application/json" \
-d '{"kind":"savings","amount":500000,"months":12,"annualRatePct":4}'Without payment this returns 402 with x402 payment requirements; an x402 client pays $0.01 USDC and retries.
{
"basisYear": 2026,
"currency": "KRW",
"disclaimer": "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.",
"source": "https://kkuldogu.com",
"tool": "deposit-interest",
"input": {
"kind": "savings",
"amount": 500000,
"months": 12,
"annualRatePct": 4
},
"result": {
"maturityAmount": 6109980,
"principal": 6000000,
"interestBeforeTax": 130000,
"interestTax": 20020,
"interestAfterTax": 109980,
"equivalentDepositRatePct": 2.17
}
}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