Introduction

One of the most fundamental documents in commercial practice is the invoice. Article 229 of the Turkish Tax Procedure Law No. 213 (“TPL”) defines an invoice as “a commercial document issued by the trader who sells goods or performs services to the customer, in order to indicate the amount owed by the customer in return for the goods sold or services rendered.” Although the Turkish Commercial Code No. 6102 (“TCC”) does not provide an explicit definition of an invoice, Article 21 thereof treats invoices as evidentiary instruments subject to an eight-day objection period with respect to the legal relationship between the parties.

For an invoice to be considered legally valid, it must contain certain mandatory elements prescribed under the TPL. In practice, however, parties frequently include optional clauses in invoices in addition to these statutory elements. Clauses stipulating the application of late interest in case of late payment (“Late Interest Clauses”) and clauses designating a competent court in the event of a dispute (“Jurisdiction Clauses”) fall within this category. The legal validity and binding effect of such clauses remain a matter of doctrinal and judicial debate.

The Approach of Turkish Courts to Optional Clauses in Invoices

In commercial life, parties may conduct their business relations either based on written agreements or established commercial customs developed over time, or, in some cases, without any written agreement or settled commercial practice at all. Within such relationships, invoices exchanged between the parties may contain not only records relating to the amount of the debt but also various optional clauses reflecting the unilateral intent of the issuing party. Indeed, practice demonstrates that invoices may include provisions concerning matters such as late interest or competent jurisdiction, and in this respect, invoices may -depending on the circumstances of the specific case- assume a function approaching or supplementing that of an agremeent.

Validity of Late Interest Clause

There is consensus that where a written agreement between the parties exists, or where an established commercial practice has developed, allowing for the charging of late interest, such interest may be claimed based on an invoice containing an unobjected late interest clause. However, in cases where neither a written agreement nor an established commercial practice exists, and where the late interest clause inserted into the invoice is not objected to within the period specified under Article 21/2 of the TCC, the question of whether late interest may nonetheless be claimed was conclusively settled by the decision of the General Assembly on the Unification of Judgments of the Court of Cassation dated June 27, 2003, with the number 2001/1 E. 2003/1 K. In this landmark decision, the court held that even where a valid commercial relationship exists between the parties, the unilateral insertion of a late interest clause into an invoice and the failure of the recipient to object within eight days merely results in the finalization of the invoice content as an evidentiary document. Such silence does not give rise to a right to claim late interest from the counterparty. By this ruling, the court eliminated the divergence of opinion among the Civil Chambers of the Court of Cassation.

Validity of Jurisdiction Clause

With respect to jurisdiction clause, in the Court of Cassation’s 11th Civil Chamber’s decision dated May 6, 2024, with the number 2023/47 E. 2024/3595 K., emphasized that for a valid jurisdiction agreement to exist, the cumulative conditions set forth under Articles 17 and 18 of the Turkish Code of Civil Procedure No. 6100 (“CCP”) must be satisfied. Accordingly, a jurisdiction agreement must be concluded in written form, arise from a specific or determinable legal relationship, and reflect a clear and mutual concurrence of intent between the parties regarding the competent court or enforcement office. In the decision, the court explicitly held that a jurisdiction clause unilaterally inserted into an invoice by the creditor, lacking the debtor’s explicit and written acceptance, does not constitute a mutual and freely formed agreement. Consequently, such a clause cannot be regarded as a valid jurisdiction agreement within the meaning of the CCP.

Analysis

Given the speed-oriented and pragmatic nature of commercial life, invoices are often enriched with optional clauses such as late interest and jurisdiction provisions, thereby extending their function beyond that of a mere debt instrument. Nevertheless, attributing an “agreement-like” function to invoices does not render such clauses legally binding in all circumstances. The jurisprudence of both courts clearly demonstrates that optional clauses unilaterally inserted into invoices produce only limited legal effects unless they are supported by an explicit, mutual, and written concurrence of intent between the parties. Accordingly, while the practical convenience of invoices remains undeniable for commercial enterprises and traders, any optional clauses intended to give rise to legal consequences must be firmly grounded in a contractual framework.