VAT Calculator
VAT-inclusive to exclusive and exclusive to inclusive. 1%, 10% and 20% are preset; net amount and VAT amount instantly.
Time elapsed
—
Late Payment Interest Calculator
A payment term surcharge (vade farkı) is the amount added in return for collecting a receivable after its due date or for selling on credit instead of for cash, and it is calculated with the formula Amount × Monthly rate ÷ 100 × Days ÷ 30. This tool answers two questions at once: how much surcharge you can ask for today on an overdue invoice, and what price to quote when spreading a cash price over payment terms. It works out the number of days from the dates and also shows the VAT on the surcharge separately.
Late Payment Interest Calculator
Surcharge
—
—
Total to collect
—
Surcharge + VAT
—
amount to put on the invoice
The calculation is done in your browser and no data is sent. The tool treats a month as 30 days; if your contract provides for an annual rate or a 365-day count, convert the rate accordingly. Results are for information only; consult your accountant for invoicing and enforcement proceedings.
Calculation formula
Vade farkı: Anapara × (Aylık oran ÷ 100) × (Gün ÷ 30) Toplam: Anapara + Vade farkı Vade farkının KDV'si: Vade farkı × KDV oranı ÷ 100
Example: ₺25,000 that is 45 days late
If you work with a monthly surcharge rate of 4%, the calculation is: 25,000 × 0.04 × (45 ÷ 30) = ₺1,500. The total you would ask the customer for is ₺26,500, and the daily surcharge is ₺33.33.
Knowing the daily amount helps in negotiation: the answer to "should I wait one more week?" is ₺233 here. Talking about the surcharge per day creates clearer collection pressure than waiting for month-end.
Who sets the surcharge rate?
First and foremost, the rate is the one you set and the other party accepts. For it to be valid, the surcharge must be stated in writing beforehand in the contract, the order or on the invoice — a surcharge added unilaterally after delivery is open to dispute.
If there is no written rate, the default interest set by law for commercial transactions applies. Because this rate changes periodically, we do not put a fixed figure here; confirm the current rate with your accountant and enter it in the field above.
Practical tip: write the rate in one sentence in the invoice footnote — "A monthly surcharge of …% applies to amounts not paid by the due date." This single line ends all later arguments.
Is VAT charged on the surcharge?
Yes. Under Turkey's Value Added Tax Law the surcharge is part of the taxable base; that is, a separate invoice is issued for the surcharge and the VAT rate applicable to the original goods or service is applied. If you sold goods subject to 20% VAT, you apply 20% to the surcharge as well.
The "Surcharge + VAT" box above gives the total you will put on the invoice. If you are unsure of the VAT rate, you can see the taxable amount and the tax amount separately with the VAT calculator.
Before calculating a surcharge: who owes how much, and since when?
A surcharge is an outcome; the real job is to see overdue receivables in time. If the due date isn't recorded, by the time you notice the delay the problem has already grown.
If you don't keep your receivables anywhere yet, start with the free account ledger tracking Excel template: the due date column automatically marks late rows as "OVERDUE". We explained what an account ledger is and how it works in our account ledger guide; if you want to move debt-and-credit tracking from a notebook to an app, caritakipprogrami.com covers the topic from the software side.
Frequently asked questions
How is a payment term surcharge calculated?
The principal is multiplied by the monthly surcharge rate and scaled by the number of elapsed days divided by 30: Principal × (Monthly rate ÷ 100) × (Days ÷ 30). With a 4% monthly rate, the 45-day surcharge on ₺25,000 is ₺1,500.
Are a payment term surcharge and late-payment interest the same thing?
In practice the same calculation is used; both ask for money for the elapsed time. The difference is in the basis: a surcharge rests on a rate agreed beforehand between the parties, while default interest rests on the rate set by law. If the contract has a rate, the surcharge applies; if not, statutory interest applies.
Can I ask for it if the invoice doesn't state a surcharge?
If there is no written rate, you cannot impose a rate of your own choosing; in that case the default interest set by law for commercial transactions applies. That is why it is best to write the rate on the invoice and order form from the start.
Is a separate invoice issued for the surcharge?
Yes, a separate invoice is issued for the surcharge and the VAT rate of the original transaction is applied. The tool's "Surcharge + VAT" box gives the total of this invoice.
Why does the tool count a month as 30 days?
In Turkey the surcharge is mostly discussed as a monthly rate, so the day count is divided by 30. If your contract uses an annual rate and a 365-day count, divide the annual rate by 12 to convert it to a monthly rate.
Are the amounts I enter saved?
No. The calculation is done entirely in your browser; the principal, rate and dates are not sent to any server.
Related calculators
Profit Margin Calculator
From purchase price to selling price, from selling price to margin. It shows markup on cost and margin on sales separately.
To keep this calculation in Excel
Customer Account Tracking Excel
A statement table that tracks the debit–credit balance per customer or supplier account across all transactions and gives due-date warnings.
Store Credit Ledger Excel
A digital ledger that automatically calculates, per customer, the credit extended, the amount paid, the remaining balance and the number of days overdue.
Search terms: payment term surcharge calculationhow to calculate payment term surchargelate payment interest calculationcredit sale price calculation
Last updated: September 10, 2026