Tax Calendar: Monthly Filing and Payment Deadlines for Companies

Every company has at least two appointments with the tax office each month: the withholding and social security premium return (muhtasar) on the 26th and the VAT return on the 28th. The tax calendar is the official schedule published by the Revenue Administration (GİB) showing which return, notification and payment taxpayers must complete by which deadline. Every three months, advance (provisional) tax is added to this schedule, and once a year the corporate income tax return. In this article, we have compiled, month by month, the dates a company subject to corporate income tax faces throughout 2026.

You do not need to memorize the dates, but you do need to understand the logic behind them. When a deadline falls on a weekend or a public holiday, the date shifts; sometimes the administration also extends the deadline. The table and explanations below show these shifts as well.

What is the tax calendar, and why should companies follow it month by month?

The tax calendar is the official list showing the deadlines for filing and payment obligations period by period. Its importance for companies is this: there are several returns within the same month, and each has a different deadline. Missing a date creates the risk of penalties and late payment interest, even if the tax itself was calculated correctly.

The Revenue Administration (GİB) publishes the calendar on its website in daily and monthly views. The annual calendar can also be downloaded. We advise our clients to check the calendar not just once at the start of the year, but again on the first working day of every month, because circulars published during the year may change certain dates.

Following the calendar also determines when your accounting records need to be closed. If you will file the muhtasar return on the 26th, payroll must be finalized at least a few days earlier. For VAT, invoices and deduction documents must likewise reach accounting before the month closes.

Which taxes do companies have to file?

The taxes that a limited liability company or joint stock company subject to corporate income tax must regularly file fall under four main headings: VAT, the withholding and social security premium return (muhtasar), stamp duty, and advance and annual corporate income tax. Depending on the line of business, additional items such as accommodation tax, tourism contribution or special consumption tax may also apply.

VAT return: the 28th of every month

The value added tax return (the return comparing the VAT charged on sales with the VAT paid on purchases) is filed by the 28th of the following month for companies taxed on a monthly basis. Payment is made on the same day. The Revenue Administration (GİB) calendar also contains separate lines for taxpayers filing quarterly; most companies, however, file monthly.

There is also VAT Return No. 2. This return is for companies that pay VAT as the responsible party on purchases subject to VAT withholding (partial withholding) and on services received from abroad. Its deadline is generally the 25th of the following month.

Withholding and social security premium return (muhtasar): the 26th of every month

The withholding and social security premium return (muhtasar) (the monthly return in which the employer reports the taxes it withheld from payments such as wages, rent and self-employment fees together with Social Security Institution (SGK) premium information) is filed by the 26th of the following month. According to the Revenue Administration (GİB) definition, this return covers withholdings made under Article 94 of the Personal Income Tax Law and Articles 15 and 30 of the Corporate Income Tax Law.

Stamp duty: the same day as the muhtasar

Companies with a continuous stamp duty liability also file and pay stamp duty paid against receipt by the 26th of the following month. Documents such as contracts, lease agreements and payrolls give rise to this tax. For this reason, planning stamp duty together with the muhtasar return is a practical approach.

Advance tax and corporate income tax

Advance tax is corporate income tax paid in advance on the current year’s earnings in quarterly periods. It is filed and paid by the 17th of the second month following the month in which the period closes. According to the Revenue Administration (GİB), advance tax paid is offset against the corporate income tax calculated on the annual return.

The corporate income tax return, on the other hand, is filed from the first day until 23:59 on the last day of the fourth month following the month in which the accounting period closes. For companies that use the calendar year as their accounting period, this means April. The tax is paid by the end of the month in which the return is filed.

Tax calendar 2026: a 12-month filing calendar for companies

The filing calendar below is based on a corporate income tax payer filing monthly VAT and monthly muhtasar returns. The dates are taken from the Revenue Administration (GİB) tax calendar; deadlines that fell on a weekend or holiday and shifted are shown in their shifted form.

VAT and muhtasar returns for the December 2026 period and the fourth advance tax period of 2026 move to the 2027 calendar. The corporate income tax return for the 2026 accounting period is also filed in April 2027.

You can read this table like a monthly tax calendar: each row shows the days for which your accounting team must be ready in that month. If your company has specific items (such as accommodation tax, tourism contribution or special consumption tax), add them separately from the GİB calendar.

Why do tax filing dates shift?

Tax filing dates change for three reasons: the deadline falling on a weekend, a public holiday, and an extension granted by the administration. The first two come from the law; the third is announced by circular. When reading the calendar, knowing why each date is where it is helps prevent planning mistakes.

Under Article 18 of the Tax Procedure Law (VUK), public holidays are included in the period; however, if the last day of the period falls on a public holiday, the period ends at the close of business on the first working day following the holiday. An example from 2026: the deadline for January VAT, February 28, fell on a Saturday, so the period shifted to Monday, March 2. Because May 17 was a Sunday, first-period advance tax also moved to May 18.

Religious holidays are subject to the same rule. The regular deadline for April 2026 VAT, May 28, fell during the Eid al-Adha (Kurban Bayramı) holiday, and the period first shifted to Monday, June 1. The Revenue Administration (GİB) then, with VUK Circular No. 199, extended the April muhtasar, stamp duty and accommodation tax returns to June 3 and the VAT return to June 5, 2026.

The same circular did not extend the deadline for VAT Return No. 2, which remained May 25. (October 2026 update: because this extension was made after the article was first published, it was added to the table later.)

There is also the fiscal holiday. Under Law No. 5604, a fiscal holiday applies every year between July 1-20, and filing periods whose last day falls within this range are deemed extended by seven days from the end of the holiday. Since the 26th and 28th of the month generally fall outside this range, companies’ monthly calendars are not affected in most years.

Are Form Ba-Bs still filed?

No. Published in the Official Gazette of September 25, 2024, the Tax Procedure Law (VUK) General Communiqué No. 565 discontinued Form Ba and Form Bs notifications as of the September 2024 period. For this reason, there is no Ba-Bs line in the 2026 tax calendar.

Note also that the previous communiqués continue to apply to notifications for earlier periods. In practice, we still hear the question “Is there a Ba-Bs at the end of the month?”; in teams working with an old checklist, this item can create an unnecessary workload.

e-Ledger berat and tax certificate: the quiet items on the calendar

There are two obligations that do not involve a monthly return but still have a deadline. The first is uploading e-Ledger berats (the approval file uploaded to GİB that shows the integrity of the electronic ledger). For entities that opted for monthly uploading, the Revenue Administration (GİB) calendar shows, for example, August 14, 2026 for the April 2026 berats and November 16, 2026 for the July 2026 berats. Dates differ for companies that chose to upload by advance tax period.

The second is the tax certificate (vergi levhası). Capital companies had to obtain their tax certificates for 2025 from the Digital Tax Office by June 1, 2026. This takes a few minutes, but it is easily forgotten when it is not on the calendar.

Additional dates for foreign-owned companies

The calendar of foreign-owned companies includes a few more items that differ from those of domestic companies. Rather than adding them to the main table, we recommend tracking them as a separate control line:

• Beneficial ownership notification form: Corporate income tax payers submit this form as an attachment to their advance tax returns and annual corporate income tax return. When the shareholding structure changes, the form must also be updated.
• Transfer pricing form: Companies that buy or sell goods or services with related parties (e.g., a parent company abroad) submit the transfer pricing form as an attachment to the corporate income tax return.
• Payments abroad: License, consultancy or service fees paid to a company abroad may give rise to withholding tax on the muhtasar return and to VAT payable as the responsible party on VAT Return No. 2.
• Country-by-country reporting: For companies that are members of a multinational group, the GİB calendar shows June 30, 2026 as the deadline for the notification form for 2025 and December 31, 2026 as the deadline for the report.

The reporting calendar for the parent company and the filing calendar in Turkey often do not overlap. Our team of experts combines the two calendars into a single closing plan and spreads out the month-end workload.

The calendar mistakes we see most often in practice

The most common mistake we encounter among our clients is assuming that VAT and muhtasar are due on the same day. A two-day difference may seem small, but in the payment plan the 26th and the 28th are separate cash outflows. The second common mistake is carrying a shifted date over to the next month: because the VAT deadline shifted to the 30th in March, it is wrong to expect the 30th in April as well.

The third mistake is treating advance tax as “a small interim return.” Advance tax is the portion of annual corporate income tax paid in advance and requires the period’s profit to be calculated correctly. If inventory, depreciation and provision entries are incomplete, the advance tax base will also be wrong.

Month-end checklist to stay on top of the tax calendar

The steps below offer a workflow that can be repeated every month for the taxes companies must file:

1. On the first working day of the month, open the GİB tax calendar and enter that month’s deadlines into your own calendar.
2. Confirm by the 10th of the month that all sales and purchase invoices have reached accounting.
3. Finalize payroll, rent and self-employment payments at least three working days before the muhtasar deadline.
4. Enter the payment amounts for the 25th, 26th and 28th separately in your cash plan.
5. In advance tax months (February, May, August, November), close the period-end entries in the first week of the month.
6. After the returns are filed, save the accrual slips and payment receipts in the period folder.

You can run this workflow with your accounting team or through outsourcing. If you would like to design your bookkeeping and return preparation together, our general accounting services are shaped around this need. You can find our other articles on taxation in our Tax Legislation category. If you are curious about our working model, you can visit our Why Akal CPA page, and for general questions, our frequently asked questions page.

The only official source for current dates is the Revenue Administration (GİB) tax calendar page. When a circular is published during the year, the date in the calendar is updated as well; for this reason, we recommend checking the page itself rather than a PDF you have saved.