The principle that no one may be tried or punished twice for the same act (ne bis in idem) protects against renewed criminal proceedings concerning the same person and the same material facts after a final criminal decision. The principle concerns not only the enforcement of a second penalty but also re-prosecution. However, the combination of two sanctions is not in itself a violation; the criminal nature of each proceeding, the identity of the act, finality and sufficient connection are assessed together. [1–4]
This article is for general information. The relationship between tax, disciplinary, administrative sanction and criminal files cannot be resolved by looking only at the names of the decisions.
Under what conditions does ne bis in idem apply?
The principle is examined by the Constitutional Court (AYM) as part of the right to a fair trial in Article 36 of the Constitution. Article 4 of Protocol No. 7 to the European Convention on Human Rights (ECHR) also sets out this guarantee. For Türkiye, the Protocol's date of entry into force is August 1, 2016; its application in time must be examined separately. [1; 2; 5]
The examination first determines whether the same person is involved. An administrative sanction against a company and a criminal case against its manager may not give rise to the same assessment, because they concern different persons. The examination then looks at the actual nature of the proceedings, the finality of the decisions and the identity of the act. Calling a measure "administrative" does not by itself exclude its criminal nature.
Same offence name, different act
An event may be labelled with different statutory provisions. For this principle, comparing offence names alone is not enough; the place, time, conduct and material facts matter. Conversely, independent acts committed on different dates under the same offence name may exist. Separate prosecution of such acts is not an automatic violation. [4; 5]
In a defence, indictments, penalty notices and reasoned decisions should be compared. Instead of saying "both files concern the same matter", the defence should show which specific conduct is being charged a second time. If there are different victims, periods or claims of continuing conduct, these are discussed expressly.
Final decision and retrial
As a rule, the guarantee is assessed on the basis of a final, or res judicata, criminal decision on the merits. An ordinary appeal or cassation review of a decision that is not yet final is supervision within the same proceedings. Such a review is not treated as a prohibited new trial merely because the case goes before a second court. [2; 5]
Article 223(7) of the Code of Criminal Procedure (CMK) provides for the dismissal of a case where a judgment has already been given, or a case already brought, against the same accused for the same act. Thus, alongside a final judgment, domestic law also protects against a duplicate case that is still pending. CMK Article 172(2) sets out specific conditions for bringing a new case after a decision of non-prosecution. These two provisions do not govern the same stage. [3]
Exceptions to reopening
New or subsequently discovered facts, or essential defects in the earlier proceedings, may make reopening possible under the statutory conditions. Article 4(2) of Protocol No. 7 separately regulates this field. An extraordinary remedy does not give unlimited power to retry a case; the statutory conditions must actually be met. [2]
Therefore, where a final decision exists, it should not simply be said that "nothing more can be done". It must be determined whether the new process is an extraordinary remedy, supervision within the same file, or an independent second prosecution.
Can administrative sanctions and criminal proceedings run in parallel?
In some areas, the same event may be the subject of administrative and criminal proceedings with different aims. However, fully independent repetition of two processes may impose an excessive burden on a person. The material and temporal connection between the processes, the sharing of evidence, limits on repetition, foreseeability and the proportionality of the total sanction are all important. [5]
Saying only "one is tax, the other is criminal" is not sufficient. In addition to the difference in the legal interests protected, it must be shown how the two mechanisms actually operate together. A process that begins long after the other has ended, collects the same evidence again from the start and ignores the earlier sanction may raise a different problem.
Ünal Gökpınar and later norm review
Ünal Gökpınar, B. No: 2018/9115, March 27, 2019: In this decision, the General Assembly of the Constitutional Court assessed tax and criminal proceedings and found no violation in the concrete case. The Court accepted the material identity of the act but evaluated the different purposes of the proceedings. This decision should not be read as meaning that a tax penalty and a criminal conviction may always be applied together without limit. [4, §§ 50–58]
In its norm-review decision E.2019/4, K.2021/78, November 4, 2021, the Constitutional Court elaborated on the importance of safeguards that ensure elements of different proceedings which affect one another are taken into account. Later assessments should take this development into account. A short summary of an older decision does not replace a current review of connection and integrity. [5]
The Mehmet Yalçın decision: even where the second judgment was set aside
In Mehmet Yalçın, B. No: 2022/95759, April 21, 2026, the Constitutional Court examined a second trial concerning the same conduct for which a penalty had already been imposed. The reversal of the second conviction for the benefit of the law and the dismissal of the case did not fully remedy the retrial suffered in the concrete case. The Court found a violation and awarded non-pecuniary damages. [6, §§ 27–32]
The decision clearly shows that protection is not limited to preventing the enforcement of a second penalty. The duplication must be identified in time. However, the amount of compensation in that decision is not a tariff that can be applied automatically to other files; the individual process and the redress are assessed.
Comparison table of the two files
| Criterion | Information to look for in the first file | Information to look for in the second file |
|---|---|---|
| Person | The natural or legal person about whom a decision was made | Whether it is the same person |
| Act | Date, place, conduct, event and period | Overlapping and different material facts |
| Criminal nature | Purpose and severity of the sanction | The actual nature of the second sanction |
| Finality | Decision, notification and finality record | Date on which the new proceeding began |
| Connection | Shared evidence and the assessment made | Consideration of the earlier proceeding |
| Total outcome | Penalty and other burdens | Offset, balancing and duplicate burden |
The table should not be used merely to show that the same article numbers appear. Each difference must be explained in legal terms. If the prosecution alleges a new period or new conduct, it must be compared with the scope of the earlier judgment. If the subject of the second proceeding was never decided in the first judgment, the outcome may be different.
How is it raised in ordinary proceedings?
In the criminal file, information about the earlier judgment or the pending case should be submitted without delay, and a request should be made for the relevant file to be obtained. The finality endorsement, indictment, judgment and narrative of events should be provided together. Writing only the UYAP file number may not be enough to show that the act is the same. The appropriate request is stated expressly under CMK Article 223(7). [3]
In an administrative sanction or tax process, the rules on competence and time limits of the relevant branch of jurisdiction apply. Filing a petition in the criminal file does not automatically preserve the time limit for a tax lawsuit. Connected files may be reported to all relevant authorities, but it cannot be assumed that one file will automatically be treated as a ground for suspension.
In appeals, the court's answer on the identity of the act or the connection between the proceedings must be addressed. The failure to take the earlier sanction into account, the burden caused by repeated evidence and the time gap must be made concrete. The objection should not be reduced to a list of constitutional provisions.
Applications to the Constitutional Court and the ECtHR
Before applying to the Constitutional Court, the relevant effective remedies must be exhausted. As a rule, a thirty-day period applies. It is also determined which of the two files, and which complaint, has reached its final stage. The finality of the first file is not in every case the event that starts the time limit for an application to the Constitutional Court; the complaint must be linked to the second process and the violation that arose from it. [7]
Lawyers may apply through the UYAP Attorney Portal. The documents of both files, a timeline, earlier objections and the responses to them are submitted. The finding of a violation, the removal of continuing consequences and any compensation claim are justified. The application itself does not automatically stop the second proceeding. [7; 8]
European Court of Human Rights (ECtHR): Article 4 of Protocol No. 7 governs proceedings within the judicial jurisdiction of the same State. It cannot be assumed that the same judgment applies directly to proceedings in two different countries; international conventions and national law must be examined separately. For the ECtHR, the general four-month time limit and the requirement to exhaust domestic remedies must also be observed. [2]
The article on applications to the Constitutional Court in criminal cases completes the picture of the relationship between the form and the ordinary remedies.
A comparative approach to tax sanctions
The comparative study by Fatma Bülbül Sanay and Adnan Gerçek shows that tax and criminal proceedings concerning the same act are regulated by different procedures in different countries. For this reason, applying a solution from another country directly to a file in Türkiye is not correct. For Türkiye, current legislation, the Constitutional Court's constitutional assessment and the Convention standards must be considered together. General classifications in legal doctrine do not replace an examination of the connection between concrete proceedings. [9]
How should files be compared in a duplicate-proceedings objection?
First, the identity of the person and of the material facts is examined
The use of different offence names for the same investigation subject does not necessarily show that the acts are different. The time, place, victim, means used and conduct attributed to the person are examined together. Conversely, separate conduct on different dates within the same commercial relationship is not treated as a single act merely because it is similar. The comparison should start from the material facts described in the indictments and decisions, not from abstract offence names. [3; 4; 6]
Where a company has been subjected to an administrative sanction and its manager faces personal criminal liability, the identity-of-person condition must be considered separately for each. This distinction is particularly important in tax and regulatory sanctions. The applicant should set out in a table who was subject to which proceeding. Sanctions against different persons should not be presented as the same person being punished twice.
Finality of the first decision and the timing of the second act
The case number of the first file, the type of decision, its finality and the date on which the second act began are all necessary. CMK Article 223(7) also covers a case already brought, in addition to a prior judgment. The Convention guarantee regarding the conditions for a final judgment and the protection under national law for a case that is pending should not be confused within the same narrative. The national provision may itself be the basis for an express request for dismissal in the concrete case. [2; 3]
A decision of non-prosecution and an acquittal are not procedurally the same. The conditions for bringing a new case after an earlier decision of non-prosecution are assessed under CMK Article 172(2) and the related procedural provisions. Instead of merely showing that an earlier decision exists, the new evidence relied on, the judicial permission required and the legal basis for restarting the proceedings should be examined. Likewise, an ordinary appeal provided for by law is not automatically a prohibited second prosecution. [3]
The connection between tax and criminal proceedings must be made concrete
Where an administrative sanction and criminal proceedings coexist, it is examined why they are regarded as complementary, how the evidence was used, the time relationship between the processes and the total burden. That the two authorities have different names or pursue different purposes is not in itself a sufficient explanation. Likewise, closeness in dates alone does not prove a material connection. The reasons given in the decisions and the sanctions imposed are assessed together. [4; 5]
If it is claimed that one sanction was taken into account in the other, the petition should show where and how this was done in the decision. Rather than saying "two penalties were imposed", the application should explain why the second process created an independent and repetitive burden. The date of the Constitutional Court decision relied on and later developments in case law should also be explained.
If the second decision was set aside, what harm continues?
The Mehmet Yalçın decision shows that the subsequent annulment of a second judgment does not in every case remedy the applicant's harm. The examination should not be reduced to the outcome of the last decision. The retrial itself, the time elapsed, the effect of enforcement and whether redress was provided are all assessed. However, an automatic compensation outcome cannot be drawn after every reversal decision. The applicant must concretely set out the continuing harm and the redress sought. [6]
Protection is not limited to preventing the enforcement of a second penalty
The guarantee against being tried twice cannot be reduced to the problem of collecting two fines or enforcing two prison sentences. Where its conditions are met, being subjected again to criminal proceedings for the same person and the same act after a final criminal process is also assessed. Therefore, the absence of a conviction in the second file does not mean that the objection is in every case premature or meaningless. It must be specified which act gives rise to a new criminal process and when the first decision became final. [1–3, 6]
In the Mehmet Yalçın decision, the later annulment of the second judgment did not by itself remedy the duplicate proceedings that had already taken place. The decision shows that remedy should not be assessed only by looking at the latest status of the file. The applicant should explain when the second process began, how long it lasted, and whether the violation was acknowledged and properly remedied. On the other hand, it cannot be said that an applicant's status automatically continues after every quashing or annulment decision; the nature of the redress provided is examined. [6]
When identifying the same act, events are compared, not names
The use of different offence names in two files does not definitively show that the material facts are different. The time, place, subject matter and conduct of the person must be compared. Likewise, the existence of the same offence name does not turn independent conduct on different dates into a single act. The applicant must show, by reference to the judgment and the indictment, which event the first decision covers. The narrative in the second file should be examined side by side with this framework. [2, 3, 6]
For example, transactions and statements relating to different periods may be discussed under the same legal heading, but whether they form the same material event is determined separately. The claim that one process is a continuation of another should not rest merely on the parties or the institution being the same. Date ranges, transaction numbers and the concrete conduct in the file should be compared. Submitting only two file numbers without this work leaves an essential element of the claim incomplete.
Why is the identity of the person examined separately?
Where a sanction is applied to a company and a criminal case is brought against a natural person, the legal identity of the parties may not be the same. Being a partner or representative of a company does not create complete identity with the company's legal personality. However, it is also not sufficient to end the examination by looking only at the names in the sanction document. The person to whom the sanction was directed and the relevant legal status must be explained. The applicant must set out the two criminal processes conducted against himself or herself. Personal harm cannot be established automatically by relying on another person's decision.
On what information is the close-connection defence reviewed?
When two processes, such as a tax sanction and a criminal case, are conducted together, merely mentioning different purposes is not enough. It is examined whether the processes complement each other, how information and evidence were evaluated, the time relationship and the total burden. A file that runs for years without the knowledge of another is not the same as processes that advance as parts of a coordinated arrangement. A close-connection claim must be shown through concrete acts. [4, 5]
Reading the Ünal Gökpınar decision together with norm-review decision E.2019/4, K.2021/78 is useful here. An explanation pointing to different purposes should not be turned into a formula that automatically makes every dual sanction system lawful. Likewise, the fact that two separate authorities acted is not in itself proof of a violation. The examination requires revealing the material and temporal relationship between the relevant processes. [4, 5]
When preparing a request, it may be shown how evidence collected in the first file was used in the second, whether the earlier sanction was taken into account, and the dates of the acts. If the applicant argues only that the total sanction is heavy, the elements of a proportionality complaint must be separated from those of a duplicate-proceedings complaint. Not every heavy sanction is a violation of ne bis in idem, and not every duplicate-proceedings problem is considered remedied merely by reducing the amount of the penalty.
Final decision and the exception for reopening
Reviewing a decision within an ordinary appeal is different from starting a new process on a decision that has become final. A claim of a second proceeding cannot be properly established without showing that the first decision has become final. The finality endorsement, the appellate decision and notification records are therefore important. The removal of a file from the register, the closing of an investigation, and the finality of a conviction or an acquittal should not be assumed to have the same legal effect. [2, 3]
The exceptions for reopening under Protocol No. 7 do not give unlimited power to hold new proceedings on the same event. If new facts, or a fundamental defect affecting the outcome of the earlier process, are alleged, this must be assessed within the lawful procedure. Mere dissatisfaction with an earlier outcome is not an adequate explanation. The petition must set out the reason for relying on the exception, the nature of the information said to be new, and its relationship to the earlier decision. [2]
For more detail, see our articles on the principle of legality of crimes and penalties and the presumption of innocence and the right to protection from stigmatisation. For our firm's work in this area, see the page on Constitutional Court and ECtHR applications.
For more detail, see our article on retrial of proceedings.
Conclusion
A claim of not being tried twice arises not from the similarity of file names, but from comparing the person, the act, the final decision and the relationship between the processes. Raising a duplication early aims not only at annulling a second penalty but also at preventing an unnecessary second proceeding. The connection between administrative and criminal processes, and their total burden, must be reviewed separately.
Frequently Asked Questions
Are two separate penalties always a violation?
No. The person, the act, the criminal nature of the sanctions, finality and the conditions of connected proceedings are assessed together.
Does the principle not apply if the offence names are different?
It can apply. The identity of the material facts matters more than the name of the offence.
Does an appeal review breach the prohibition on a second trial?
An ordinary appeal forms part of the same proceedings; the mere existence of a review by another court is not a violation.
Does annulling the second penalty remedy everything?
Not in every case. The retrial itself and any consequences that have not been remedied may be examined separately.
Are a company's file and its manager's file treated as concerning the same person?
Not automatically. The addressee of the sanction must be clearly identified.
Are proceedings in two different countries subject to the same rule?
Article 4 of Protocol No. 7 governs proceedings within the same State. Cross-border situations are examined separately.
Sources and Legal Basis
[1] Constitution, Art. 36. Text.
[2] Protocol No. 7 to the ECHR, Art. 4; ECHR, Art. 35. Text.
[3] Law No. 5271, Code of Criminal Procedure (CMK), arts. 172/2, 223/7. Text.
[4] Constitutional Court, General Assembly, Ünal Gökpınar, B. No: 2018/9115, March 27, 2019. Decision.
[5] Constitutional Court, E.2019/4, K.2021/78, November 4, 2021. Decision.
[6] Constitutional Court, Mehmet Yalçın, B. No: 2022/95759, April 21, 2026. Decision.
[7] Law No. 6216, arts. 45–50. Text.
[8] Constitutional Court, UYAP Attorney Portal application guide. Guide.
[9] Fatma Bülbül Sanay and Adnan Gerçek, "Türkiye ve Seçilmiş Avrupa Ülkelerinde Vergi Ceza Hukukunda Ne Bis In Idem İlkesinin Karşılaştırılmalı İncelenmesi" ("A Comparative Examination of the Ne Bis In Idem Principle in Tax Penal Law in Türkiye and Selected European Countries"), Dokuz Eylül Üniversitesi Sosyal Bilimler Enstitüsü Dergisi, 28/3, 2026, pp. 1359–1390. Study.