Vergi Kimlik Numarası (VKN) tax ID format

Format

10 digits with no separators, hyphens, or spaces. Example: "0100478064".

Validation

The checksum algorithm validates correctness:

function validateVKN(vkn) {
  if (!/^\d{10}$/.test(vkn)) return false;
  
  let v1 = 0, v2 = 0;
  
  for (let i = 0; i < 9; i++) {
    let digit = parseInt(vkn[i]);
    let temp = (digit + (9 - i)) % 10;
    v1 += temp;
    v2 += (temp * (9 - i) + 1) % 10;
  }
  
  let checksum = (10 - (v2 % 10)) % 10;
  return checksum === parseInt(vkn[9]);
}

VAT rates and calculations

Standard rates

20%

Standard rate (KDV) for most goods and services

10%

Reduced rate (basic food products, certain services)

1%

Super-reduced rate (agricultural products, certain essential goods)

0%

Zero rate (exports, international transportation)

Exempt categories

• Financial services and insurance

• Medical and healthcare services

• Education

• Real estate leasing by individual landlords

Tax calculation

Tax calculation uses these formulas:

Tax Amount = Base Amount × Rate
Gross Amount = Base Amount + Tax Amount

When you calculate taxes, you must round all amounts to two decimal places.

Important:

Always use decimal arithmetic, not floating point, to avoid rounding errors in tax calculations.

Amount precision

Currency amounts

Two decimal places. Example: "1234.56".

Quantities

Up to eight decimal places. Example: "10.25197700".

Unit prices

Up to eight decimal places. Example: "50.53112390".

Tax percentages

Two decimal places. Example: "20.00".

Exchange rates

Two decimal places. Example: "40.73".

Date and time format

Date format

Use the YYYY-MM-DD (ISO 8601) format. Example: 2025-08-15.

DateTime format

Use YYYY-MM-DDTHH:MM:SS+03:00 to include the Turkey timezone, which is UTC+03:00 (year-round, no Daylight Saving Time). Example: 2025-08-15T20:38:09+03:00.

Issue date rules

You must:

• Never choose a date in the future.

• Submit the invoice within seven days of the issue date.

• Submit invoices promptly for best operational efficiency.

Unit of measure codes

Turkey uses UN/CEFACT codes (Recommendation 20).

The following example shows how to use these codes:

<cbc:InvoicedQuantity unitCode="C62">1</cbc:InvoicedQuantity>
<cbc:InvoicedQuantity unitCode="KGM">25.50</cbc:InvoicedQuantity>