Turkey-specific technical requirements

Vergi Kimlik Numarası (VKN) tax ID format

Format

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

Validation

The checksum algorithm validates correctness:

JAVASCRIPT

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]);
}

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:

CODE

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

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).


Code	Description	Usage
C62	Unit (piece)	Individual items
KGM	Kilogram	Weight in kg
MTR	Meter	Length in meters
LTR	Liter	Volume in liters
HUR	Hour	Time in hours
DAY	Day	Time in days
MTK	Square meter	Area in square meters
MTQ	Cubic meter	Volume in cubic meters

The following example shows how to use these codes: