Late payment interest API

Late payment interest in Vietnam: tax 0.03% a day, social insurance, administrative fines and Civil Code interest, with partial payments and rate history.

GETPOSThttps://apibox.io.vn/v1/vn-late-interest

Data & JSON▶ Try it online

Send the amount, the due_date (deadline) and either the paid_date, a list of partial payments or a to date, and choose the kind: tax (tiền chậm nộp thuế: 0.05% a day from 2015, 0.03% from 1/7/2016, kept by Luật Quản lý thuế 38/2019 and 108/2025), social_insurance (BHXH, BHYT, BHTN: 0.03% a day from 1/7/2025, Luật BHXH 2024 Điều 40), fine (administrative fines: 0.05% a day), civil (Bộ luật Dân sự Điều 357: agreed rate up to 20% a year, or 10% a year), loan_overdue (150% of the loan rate) or custom.

Days are counted like the tax authority does: from the day after the deadline to the day before the money is paid, weekends and holidays included (include_payment_day=true counts the payment day too). The period is split when the legal rate changes or a partial payment reduces the balance, and each segment shows its days, balance, rate and legal reference.

If a deadline falls on a day off it moves to the next working day: send that date as due_date. Exemptions and extensions decided by the tax office are not applied.

Parameters

Name	In	Type	Required	Default
`kind`	query\|body	string	no	`tax`	`tax`, `social_insurance`, `fine`, `civil`, `loan_overdue` or `custom`.
`amount`	query\|body	number	yes		Amount paid late (VND).
`due_date`	query\|body	string	yes		Deadline (YYYY-MM-DD).
`paid_date`	query\|body	string	no		Date the whole balance was paid.
`payments`	body	array	no		Partial payments: `[{"date":"2026-04-10","amount":50000000}]`.
`to`	query\|body	string	no		Compute up to and including this date (default today when unpaid).
`rate_percent_per_year`	query\|body	number	no		Agreed / loan rate for `civil`, `loan_overdue`, `custom`.
`rate_percent_per_day`	query\|body	number	no		Custom daily rate (e.g. BHXH periods before 7/2025).
`include_payment_day`	query\|body	boolean	no		Count the payment day too.

Example

curl "https://apibox.io.vn/v1/vn-late-interest?amount=100000000&due_date=2026-07-20&paid_date=2026-08-15" \
  -H "Authorization: Bearer YOUR_API_KEY"

const res = await fetch('https://apibox.io.vn/v1/vn-late-interest?amount=100000000&due_date=2026-07-20&paid_date=2026-08-15', {
  method: 'GET',
  headers: {
    Authorization: 'Bearer YOUR_API_KEY',
  },
});
const data = await res.json();
console.log(data);

import requests

res = requests.get(
    "https://apibox.io.vn/v1/vn-late-interest?amount=100000000&due_date=2026-07-20&paid_date=2026-08-15",
    headers={"Authorization": "Bearer YOUR_API_KEY"},
    timeout=30,
)
print(res.json())

<?php
$ch = curl_init('https://apibox.io.vn/v1/vn-late-interest?amount=100000000&due_date=2026-07-20&paid_date=2026-08-15');
curl_setopt_array($ch, [
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => ['Authorization: Bearer YOUR_API_KEY'],
]);
$response = curl_exec($ch);
print_r(json_decode($response, true));

Response

{
  "kind": "tax",
  "name_vi": "Tiền chậm nộp thuế, khoản thu khác do cơ quan thuế, hải quan quản lý",
  "name_en": "Late payment interest on tax",
  "amount": 100000000,
  "due_date": "2026-07-20",
  "calculated_to": "2026-08-14",
  "days_late": 25,
  "interest": 750000,
  "outstanding_principal": 0,
  "total_still_due": 750000,
  "segments": [
    {
      "from": "2026-07-21",
      "to": "2026-08-14",
      "days": 25,
      "balance": 100000000,
      "rate_percent_per_day": 0.03,
      "interest": 750000,
      "ref": "Luật Quản lý thuế 108/2025/QH15 Điều 16 khoản 2; Nghị định 252/2026/NĐ-CP Điều 26: 0,03%/ngày"
    }
  ],
  "payments": [
    {
      "date": "2026-08-15",
      "amount": "remaining balance",
      "balance_after": 0
    }
  ],
  "day_count": "day after due date → day before payment (inclusive)",
  "legal": [
    "Luật Quản lý thuế 108/2025/QH15 Điều 16 khoản 2; Nghị định 252/2026/NĐ-CP Điều 26: 0,03%/ngày"
  ],
  "reviewed": "2026-11-11"
}

Use cases

Add late interest to tax payment slips in accounting software
Compute interest on late social-insurance contributions
Claim Civil Code interest on overdue invoices
Check the amount on a tax office notice

FAQ

Did the 2025 Law on Tax Administration change the rate?

No. Luật Quản lý thuế 108/2025/QH15 (from 1/7/2026) keeps 0.03% a day (Điều 16.2.a); the counting period is set by Nghị định 252/2026/NĐ-CP Điều 26.

Are weekends and holidays counted?

Yes, calendar days are counted. Only the deadline itself moves to the next working day when it falls on a day off.

What rate applies to a late commercial invoice?

Civil Code Điều 357: the agreed rate (capped at 20% a year) or 10% a year. Commercial contracts may claim the average market overdue rate (Luật Thương mại Điều 306): send it as rate_percent_per_year.

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Late payment interest API

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