Firm Profile > GSG Attorneys at Law/GSG Hukuk > Istanbul, Turkey

GSG Attorneys at Law/GSG Hukuk

Turkey > Tax Tier 1

GSG Attorneys at Law/GSG Hukuk is a specialist tax firm, whose experts have extensive past experience with Turkish tax authorities and Big Four auditors. Affiliated with PricewaterhouseCoopers, the firm advises and represents major international clients across multiple industries, including defence, financial services, automotive, technology, and digital services, handling Turkish tax investigations, negotiations with tax authorities, and litigation. The team is led by highly experienced tax practitioner Zeki Gündüz, a hugely respected figure within the sector, alongside Ezgi Turkmen, who has a notable specialism in the digital economy space and corporate tax disputes.

Practice head(s):

Zeki Gündüz; Ezgi Turkmen


‘Analytical thinking, fast and true judgement.’

‘Key strengths are: customer-focused approach;  technical know-how;  broad customer and case experience.’

‘A strong, pragmatic tax team.’

‘Ezgi Turkmen is solution oriented.’

Zeki Gunduz is a strong trusted advisor.’

‘We would recommend GSG to any client in need of tax advisory services. We are always impressed with their technical abilities and level of professionalism. They are committed to delivering exceptional work and keeping a good working relationship with all parties.’

‘We work with GSG for tax litigation cases, They are a most capable team in the tax litigation area. They know the theory, practice and business needs and are very strong in their written and verbal representation of our company.’

Turkey > Commercial, corporate and M&A Tier 4

An affiliate of PricewaterhouseCoopersGSG Attorneys at Law/GSG Hukuk has international capabilities and a broad range of expertise across transactional work, corporate restructuring, and regulatory issues, including tax considerations. The firm acts for corporates in fields including energy, electronics, and manufacturing, reflecting broad expertise and regulatory capabilities. The team is led by the 'deeply experienced and agile' Nilgün Serdar Şimşek, who has considerable experience of transactions and corporate governance issues.

Practice head(s):

Nilgün Serdar Şimşek


‘The team is deeply experienced and agile, very thorough, well organized and client focused . We are very happy to work with them for years. The firm stands out in understanding the commercial interests and needs of both their clients and their counterparts, which greatly helps in getting deals closed and disputes resolved in a valuable and safe way. We recently closed a very complex and a long-standing deal together, thanks to their legal approach and communication skills. We often observe that they come up with practical solutions based on their knowledge and experience.’

‘We have previously worked with GSG for our investment in the energy market in Turkey and they have counselled us during the share purchase agreement negotiations for our investment. We do believe that GSG Team holds the unique skill of providing high quality legal advice while understanding the business needs involved.’

‘The strength of the team comes from the depth of their legal knowledge, their vast experience especially in the field of M&A and diligent and meticulous handling of their projects.’

‘I worked with the GSG Corporate team for more than one project. GSG Corporate team is very practical, focusing on the needs of the client and always trying to provide solutions. They do understand the necessities of the client in a comprehensible manner and the team is always very good at communication.’

‘ The GSG team has great technical skills and they always provide quick and accurate advice. The lawyers are very committed, hardworking and experienced. They devote time and effort to understanding and getting to know your company and your needs.’

‘I have had the opportunity to work with GSG attorneys on various separate occasions. Mrs. Simsek and her legal team are of the highest caliber and an absolute joy to work with. We have once again engaged with them for a very complex restructuring project which included reorganization of a real estate project with our then existing partner, which is one of the preeminent group of companies in Turkey. GSG attorneys produced for us a framework agreement, a shareholders’

‘Nilgun Serdar Simsek, is the leading partner. She is open to feedback and she has been very constructive at solving any issue any time. She gives importance to team development. She had invested much at her team over the years.’

The firm: GSG Attorneys at Law / GSG Hukuk is an independent law firm established by the three name partners, Zeki Gunduz, Nilgun Serdar Simsek and Umurcan Gago, following many successful years of working together in a leading global consultancy services firm. In June 2016, Ezgi Turkmen who has been working in this business line more than 16 years, has been announced as partner in tax and customs dispute resolution team, became the fourth partner at GSG Attorneys at Law.

GSG provides solutions for a wide range of legal issues, from incorporation to complex structuring alternatives for domestic and multinational clients in a wide range of industries. GSG Attorneys at Law not only provides diligent legal services but also acts with an understanding of the economic and political environment of Turkey.

GSG offers the complete range of legal services for business in Turkey, with each partner overseeing their respective areas of expertise. Nilgun Serdar Simsek oversees corporate and commercial matters undertaken by the firm and has led a number of Turkey’s landmark M&A and structuring transactions in recent years. Tax expert Zeki Gunduz and Ezgi Turkmen, who became the new partner in the team in 2016, are lead the tax and customs advisory and dispute resolution practices. Umurcan Gago heads the banking, finance and capital markets law practice, which regularly publishes leading literature resources in these areas.

In addition to more than 40 lawyers, GSG utilises counsel expert in industry and government regulation as well as a network of tax and legal experts across 80 countries.

Areas of practice: In corporate, M&A and structuring practice, GSG is a preferred provider of corporate structuring services for local and international clients. At each stage of M&A transactions – planning, drafting, negotiations, signing and closing – GSG professionals have demonstrated their wide industry knowledge, including finance, real estate, media and entertainment, insurance, and automotive and telecommunications.

The established tax and customs dispute resolution team at GSG advises on procedures followed by tax and customs authorities and strategies to minimise risk exposure, and renders assistance by attending pre-trial hearings with tax and customs authorities. GSG lawyers are experts in the assessment and calculation of any available discounts, late interest payments and the preparation of relevant statements.

In banking, finance and capital markets, GSG advises many local and international investment and commercial banks and financial institutions on capital markets rules, investment banking products, finance regulation and international tax planning. Its experts are skilled in securities regulation, international financial transactions, derivatives laws, taxation of financial instruments, international taxation and private equity funds.

The labour team at GSG offers advisory and representation on individual and collective employment agreements, negotiation and dispute resolution, drafting employment agreements, workplace regulation and compliance, confidentiality and non-competition issues and employment termination.

The energy, mining and projects team at GSG has executed substantial projects in the mining, electricity, natural gas and renewable energy industries, proving outstanding ability in addressing government regulation and ingenuity in structuring and efficiency.

In real estate, GSG advises and represents clients on the acquisition, rental, operation, management and development of real estate, as well as applications to relevant authorities for necessary construction and land usage permits. The team also manages drafting, negotiation and signing of EPC (engineering, procurement and construction) contracts.

Data protection law is a relatively new practice for Turkey and GSG is one of the few active law firms providing professional legal assistance in this field, including addressing concerns on a case-by-case basis and helping clients, not only by answering their questions but also implementing legal requirements and best- practices through compliance programmes.

Department Name Email Telephone
Tax and customs dispute resolution Ezgi Türkmen
Tax and customs dispute resolution Yesim Dikici Orhan
Banking, finance and capital markets Umurcan Gago
Corporate, M&A and commercial Nilgün Serdar Simsek
Corporate, M&A and commercial Yavuz Dayioglu
Restructuring Nilgün Serdar Simsek
Tax advisory Zeki Gündüz
Tax advisory Gülcan Çaliskan
Labour Cagil Sahin
Labour Riza Eroglu
Real estate and construction Dilara Saatcioglu
Energy and mining projects Cagil Sahin
Energy and mining projects Yavuz Dayioglu
Family business Nilgün Serdar Simsek
Family business Yavuz Dayioglu
Data protection Ilke Fadillioglu
Data protection Ipek Okucu Taftali
Restructuring İlke Fadillioglu
Banking, Finance and Capital Markets Gizem Sozenoglu
Tax & Customs Dispute Resolution Fatma Dondar
Tax Litigations Aykut Kapusuzoglu
Tax Litigations Cemal Araalan
Photo Name Position Profile
Ms Fatma Dondar  photo Ms Fatma Dondar Fatma is working as Manager at GSG Attorneys at Law.
 İlke Fadillioglu  photo İlke Fadillioglu Senior Manager
Ms Oyku Ocal  photo Ms Oyku Ocal Senior Attorney
Ms Çağıl Sahin  photo Ms Çağıl Sahin Çağıl is working as a Senior Manager in GSG Attorneys at Law.
Ms Ezgi Turkmen  photo Ms Ezgi Turkmen Ezgi is working as a Partner in GSG Attorneys at Law.
Number of lawyers : 40
Worldwide : Part of a network of 3,000 lawyers across 80 countries
International Bar Association

CLIENT: Director


TESTIMONIAL: We have worked with a great team who tailored their expertise to our needs.

CLIENT: Finance & Accounting Manager


TESTIMONIAL: The firm focuses on our needs. They are very capable at putting themselves in our shoes; we can get accurate answers for all of our questions.

CLIENT: HR Manager


TESTIMONIAL: We highly recommend this firm to other firms. They have great experience and they are always available when we need them.

CLIENT: Finance Director


TESTIMONIAL: The firm and our company have a long-term relationship. During this time we have been very satisfied with the quality of their help.

CLIENT: Deputy General Manager

TESTIMONIAL: We are very happy to work with this team, who are experienced and highly specialised in a range of areas. They always have up-to-date information, confidence, and social capacities.

CLIENT: Territory Manager


TESTIMONIAL: Their team is a part of our team; they are very supportive, very responsive, clear, and always solve our problems.

CLIENT: Chairman of the Board


TESTIMONIAL: We have experienced a tough process with the Firm’s team, we are very content to work with them and looking forward to work together with them again.

At GSG attorneys at Law, our colleagues, clients, and others with whom we do business are treated with respect, dignity, fairness, and courtesy. We take pride in the diversity of our workforce and view it as a competitive advantage to be nurtured and expanded. Women and our young talent have considerable
influence at GSG Attorneys at Law.

Current Initiatives and Achievements

  • The working environment of GSG Attorneys at Law is free from discrimination, harassment, and retaliation.
  • We try to balance work and private life, and help others to do the same.
  • We provide a safe working environment for our people.
  • Team members can benefit from flexible work hours, working from home, or working part-time.
  • Every team member has a coach within the company who is mentoring their personal development related to both soft and technical skills.


GSG Attorneys at Law supports fundamental human rights and avoids participating in business activities that abuse human rights.

We act in a manner that minimises the detrimental environmental impacts of our business operations. We encourage our colleagues to support charitable, educational, and community service activities.