How Is Provisional Tax Calculated? Ways to Prepare Your Cash for Surprises

When provisional tax day comes round every three months, having the cash ready in the till matters a great deal to businesses. Making a profit is not enough; the profit has to have turned into cash. This is exactly where poorly managed cash flow can turn even a correctly calculated tax into a "surprise payment". In this article we have brought together everything you need to know, from how provisional tax is calculated to the 2026 period dates and practical steps to prepare your cash flow for surprises.

🚀 At a Glance

• Provisional tax is paid in 3 periods a year; each period is calculated cumulatively on top of the previous one, so amounts can change from period to period.

• Filing and payment share the same deadline — both the tax return and the payment are due by the 17th of the second month following the period.

• The biggest risk is confusing profit with cash; tax also arises on income that has been invoiced but not yet collected.

• Setting up a simple reserve system lets you meet the payment comfortably at the end of the period without straining your cash.

What Is Provisional Tax?

Provisional tax is a tax that businesses pay in advance, in three-month periods, on the profit they earn during the year. These amounts paid during the year are offset against the tax calculated on the income tax or corporate tax return filed at year end. In other words, provisional tax is your annual tax brought forward in instalments, and your cash flow needs to be ready for it.

Who pays it?

• Business income earners and self-employed professionals taxed under the actual method (income tax payers)

• Corporate tax payers such as joint-stock and limited companies

Those who only earn rental income or investment income are not liable for provisional tax.

2026 Provisional Tax Periods and Deadlines

A change made in 2022 abolished the fourth period (October-December); tax for that period is now calculated directly on the annual tax return. The periods for 2026 are as follows:

How Are Provisional Tax Rates Set?

• Corporate tax payers (Inc., Ltd.): The current corporate tax rate of 25% applies. For banks, insurance companies and financial institutions the rate is 30%.

• Special Reduction for Exporters and Manufacturers: For exporting companies the rate is reduced by 5 points to 20%, and for those engaged in manufacturing it is reduced by 1 point to 24%.

• Income tax payers (sole proprietorships, self-employed): The provisional tax rate is 15%.

Because the calculation is cumulative, it is based on total profit from January to the end of that period, and the amount you paid in earlier periods is deducted. In a quarter where your profit falls, the tax payable also falls automatically or may drop to zero.

Calculate with Üstad

Tracking the cumulative tax base and amounts that change from period to period can easily get confusing when done by hand. So rather than working out your estimated provisional tax yourself, you can use the Üstad Provisional Tax Calculator instead. Enter your profit, choose your taxpayer type and let the tool do the rest.

The Real Cause of Surprise Payments: Confusing Profit and Cash

Provisional tax is calculated on invoiced profit, regardless of whether that profit has been collected. So even a sale on credit that you have invoiced but not yet been paid for is included in the tax base. This is exactly why many businesses end up saying "we prepared the tax return correctly but could not find the cash to pay".

Practical Steps to Manage Your Cash Flow

1. Make an Estimate Before the Period Closes

Before the period ends (for example, in the middle of the last month), work out an approximate provisional tax amount based on your cumulative profit to date. An early estimate, rather than waiting for the exact figure, gives you more time to prepare.

2. Set Aside a Separate Account for Tax from Your Profit

Each month, automatically transfer a set percentage of your profit (for example, the 25% share for companies) to a separate account. At the end of the period, the amount needed for the payment is ready in this account and you do not need to touch the business's main cash.

3. Match Your Collection Schedule to the Tax Calendar

Make sure large customer collections or project payments are scheduled a few weeks before the provisional tax payment deadlines (17 May, 17 August, 16 November), not just before them. For sales on credit, it helps to set payment terms with these dates in mind.

4. Follow the Cumulative Logic

If you paid a large amount in the previous period and your profit has fallen this period, the amount you pay will also fall. Knowing this in advance stops you setting aside more cash than you need.

5. Contact Your Accountant Early

Especially in "forgotten" periods such as the 2nd period, which falls in the summer months, do not wait until the last week. An early preliminary meeting makes both the calculation and payment planning easier.

💡 Üstad Reminder: When you keep your income and expense tracking up to date in Üstad, you can see your approximate profit before the period closes and easily refine your estimates of the provisional tax amount.

What Happens If the Payment Is Neglected?

• If it is not filed on time: An irregularity penalty and late payment interest start to apply.

• If it is filed but not paid: It can no longer be offset at year end; even if the unpaid amount is written off, late payment interest is assessed from the due date to the write-off date.

Action List

• Make an estimate 2 weeks before the period closes

• Transfer the tax share of your monthly profit to a separate account

• Plan your collections on credit around the tax calendar

• Set a calendar reminder for the next period

• Meet your accountant early, before filing

❓ Frequently Asked Questions

What is the difference between provisional tax and annual tax?

Provisional tax is an amount paid in advance in three-month periods during the year. These amounts are offset against the annual income tax or corporate tax calculated at year end.

Do I have to pay provisional tax in a period where I made a loss?

Because the calculation is cumulative, if your cumulative tax base has fallen or closed at a loss, the tax payable for that period may be zero.

If I cannot pay provisional tax on time, can I make up for it at year end?

No. Provisional tax not paid on time cannot be offset on the annual tax return, and late payment interest also runs from the due date.

What happens if the filing deadline falls on a weekend?

The deadline moves to the next working day. However, if there is no official Revenue Administration (GİB) announcement, be sure to confirm this extension during filing week.

Is there a difference in rates between a sole proprietorship and a limited company?

Yes. Sole proprietorships (income tax payers) pay the first bracket rate of 15%, while limited and joint-stock companies (corporate tax payers) pay 25% (30% for financial institutions).