# Changed Your NACE Code at the Tax Office? What to Do at SGK in Turkey

> Changing your NACE code at the tax office does not update SGK. How the 26-digit workplace number, sector code and NACE change request work in Turkey.

Source: https://sinemyavuz.com.tr/en/blog/changing-nace-code-tax-office-and-sgk-turkey
Category: Payroll & Social Security
Published: 2026-09-30
Updated: 2026-09-30
Author: Sinem Yavuz, Certified Public Accountant (SMMM) — SMMM Sinem Yavuz: Finance, Accounting & Advisory Office

## Key Takeaways

- The 26-digit SGK workplace registration number contains a four-digit sector (işkolu) code, and if that code changes the number changes too. We found no rule that carries a tax office change into the SGK record automatically, so the SGK request is made separately.
- At the tax office, change notifications are due within one month of the event (Tax Procedure Law Art. 168); for SGK, the law sets no separate deadline for a NACE change.
- A wrong code no longer changes your work accident premium rate, because the short-term insurance premium is a single rate (Law 5510 Art. 81/1-c); the real risks are the OHS hazard class and sector-based incentives.

Changing the NACE code at the tax office does not change your SGK record; you file a separate request with SGK. The two agencies keep separate files, and we found no rule under which a tax office update flows into the SGK workplace file by itself. This article covers the SGK side. Online sellers choosing a code should read our [e-commerce NACE code article](/en/blog/e-commerce-nace-code-change-turkey), which we do not repeat here.

## Where Is the Sector Code in the Workplace Number?

The SGK workplace registration number has 26 digits, and a four-digit sector code (işkolu kodu) sits inside it. The number also carries the workplace's private or public nature, a unit code, a sequence number, province and district codes, a check number and a subcontractor code (Social Insurance Procedures Regulation Art. 28). SGK's March 2025 announcement states that when the four-digit code changes, the 26-digit number changes with it. The sector code is therefore part of the identifier, not just a label.

## Is the NACE Code the Same as the Sector Code?

They are linked but not identical: SGK sets a four-digit sector code and then asks for the six-digit NACE code that falls under it. According to SGK's e-Bildirge announcement, the employer selects the six-digit code under the "Sector Code Sub-class Entry" menu. If the options shown do not match the work done at the workplace, the "new workplace NACE code request" link on the e-Bildirge home page is used.

## What Changed in March 2025?

SGK converted many workplaces to NACE Rev.2.1 itself. The notice amending Annex 1 of the Workplace Hazard Classes Communiqué appeared in Official Gazette No. 32840 on 13 March 2025, and SGK converted affected employers' codes from Rev.2 to Rev.2.1 on 15-16 March 2025. Where the four-digit code changed, the 26-digit number changed too. SGK asked employers to check this in the e-SGK Employer System and to file under the new number.

## Tax Office and SGK: What Is Done Where?

The two filings are separate, as the table shows.

| | Tax office | SGK |
|---|---|---|
| What changes? | Activity (NACE) code | Sector code and NACE code |
| Where? | Digital Tax Office (activity subject change petition) or a petition to the tax office | "Workplace NACE Change Request" application (via e-Devlet and e-Bildirge) |
| Who files? | Taxpayer or authorised accountant | Employer or authorised user |
| Deadline | Change notifications within one month of the event (Tax Procedure Law Art. 168) | No separate legal deadline; we recommend filing as soon as the tax record is updated |

The Revenue Administration's Digital Tax Office guide includes an "Activity Subject Change Petition" step. For companies, the Trade Registry Gazette details of the decision are entered, or a notarised copy of the decision is attached if it was not published. The guide dates from 2019, so screens may have changed.

Tax Procedure Law Articles 157-159 list address, taxpayer status and number-of-workplaces changes and do not name the activity code. We therefore apply the general one-month rule of Article 168. Article 160 covers ceasing business, not a code change.

## Is There an SGK Deadline?

Law 5510 Article 11 requires the workplace declaration on the day you start employing insured workers. Its ten-day deadlines cover a move to another province, transfer or succession, change of company type, merger, and a new partner in an ordinary partnership; a change of activity code is not among them. Failing the Article 11 duties carries a fine under Article 102/1-(b); we found no penalty specific to a late code update. See our [SGK administrative fines article](/en/blog/sgk-administrative-fines-2026-turkey) for amounts.

## What Are the Consequences of a Wrong or Outdated Code?

A wrong code does not change your work accident premium rate today. Premiums used to follow the hazard class, but Articles 83 and 84 of Law 5510 were repealed in 2013. Article 81/1-(c) now sets the short-term insurance premium at 2.25% of insurable earnings, and the President may move it between 1.5% and 2.5%. The 2.25% figure came from Law 7524 in 2024; check presidential decisions for the current rate.

The real consequences are these:

- **OHS duties:** The workplace hazard class is tied to the NACE code in the annex to the Ministry of Labour's communiqué. With the wrong class, workplace physician, safety specialist and training duties under Law 6331 are planned against the wrong tier.
- **Incentives:** SGK's 2026 premium incentive table gives a different extra discount for manufacturing. If your recorded code does not match your real activity, that distinction becomes doubtful. We cover minimum labour cost and incentive errors in our [monthly SGK declaration article](/en/blog/minimum-labor-cost-sgk-incentives-turkey).
- **New filings:** If the registration number changed, hire and termination notices must use the new number; deadlines are in our [registration and termination article](/en/blog/sgk-employee-registration-termination-deadlines).

## Step by Step

1. Choose the six-digit code that matches what you actually do.
2. Update the activity code at the tax office and obtain the new tax certificate.
3. In the e-SGK Employer System, check your current sector code and 26-digit number.
4. If they do not match, file a request in the "Workplace NACE Change Request" application.
5. If the number changed, update payroll and declaration systems to the new number.

## Frequently Asked Questions

### I changed the code on my tax certificate. Does my SGK number change?

A tax office change does not change the SGK record by itself. If the four-digit sector code at SGK changes, the 26-digit number changes too, and that needs a separate SGK request.

### Is there a legal deadline for a NACE change at SGK?

No, Article 11 of Law 5510 sets no separate deadline for it. The tax office has a general one-month rule for change notifications (Tax Procedure Law Art. 168).

### Does a wrong NACE code raise my work accident premium?

No, the short-term insurance premium is set by law as a single rate (Law 5510 Art. 81/1-c). A wrong code can affect the hazard class, OHS planning and sector-based incentives.

## Updating the Code at Both Agencies in Order
We determine the right code for your activity, run the tax office update and the SGK request in the correct order, and move payroll and declaration records to the new number if it changed. See our [SGK services](/en/services/social-security-sgk) and [tax advisory](/en/services/tax-advisory) pages, or contact us.

## Legal Basis and Sources

Current official texts of the laws cited in this article, from the Legislation Information System (in Turkish). Regulation, circular and Official Gazette references are given where they appear in the text.

- [Law No. 213: Tax Procedure Law](https://www.mevzuat.gov.tr/mevzuat?MevzuatNo=213&MevzuatTur=1&MevzuatTertip=4)
- [Law No. 5510: Social Insurance and General Health Insurance Law](https://www.mevzuat.gov.tr/mevzuat?MevzuatNo=5510&MevzuatTur=1&MevzuatTertip=5)
- [Law No. 6331: Occupational Health and Safety Law](https://www.mevzuat.gov.tr/mevzuat?MevzuatNo=6331&MevzuatTur=1&MevzuatTertip=5)