The principles of contractual commitment (pacta sunt servanda) and freedom of contract have been accepted in our legal system. According to these principles, the contract must be applied and its provisions must be adhered to exactly as they were agreed upon at the time of the contract. In other words, even if the conditions of the contract have become more burdensome for the debtor or the balance of obligations has changed due to unforeseeable events, the debtor must fulfill their obligations exactly as stated in the contract. According to the principle of pacta sunt servanda, changes in circumstances or the occurrence of sudden and risky events do not constitute an obstacle to fulfilling the agreement. The parties enter into the contract taking into account future conditions and are obligated to keep their word. It should also be noted that the principle of freedom of contract requires that the parties be equal rights holders with each other.
If changing circumstances disrupt the natural balance of the contract, and the parties have not taken any measures for such situations, a gap in the contract will be filled by interpretation in accordance with the meaning of the contract and the will of the parties, and in compliance with the principle of good faith. (Article 1 of the Turkish Civil Code) This method of interpretation or adjustment of the contract to changing circumstances is called "adaptation of the contract."  
Demanding the adjustment of the rent amount to changing conditions throughout the duration of the lease contract is also known as a "rent adjustment lawsuit." This article focuses on the details of a rent adjustment lawsuit.
1. CONDITIONS FOR RENT ADJUSTMENT LAWSUIT
The main purpose of a rent adjustment lawsuit is to request an adjustment based on the excessive difficulty of performance, as stipulated in Article 138 of the Turkish Code of Obligations. It should be noted that a rent adjustment lawsuit can be filed for any type of lease agreement. The necessary conditions for filing a lawsuit are as follows :
In summary, an extraordinary situation that is unforeseen or unexpected is required for an adjustment lawsuit to be filed. Even if a situation can be foreseen, if the scope and magnitude of the consequences cannot be predicted in advance, the "unforeseeability" requirement is deemed to have been met. 
2. CONFLICT AND FILING A LAWSUIT
The rent adjustment lawsuit can be filed at any time without the need for a warning if the conditions in Article 138 of the Turkish Civil Code are met. This lawsuit can be filed by either the lessor or the lessee who has a legal interest in filing it.
In cases of excessive inflation, there may be a disproportionate obligation in favor of the lessor, while in cases where the rent is determined in foreign currency, there may be a disproportionate obligation and excessive performance difficulties in favor of the lessee due to high levels of devaluation between obligations in the application of the rent adjustment lawsuit. 
3. COMPETENT AND AUTHORISED COURT
According to Article 4/1 of the HMK No. 6100, regardless of the value or amount of the subject matter of the lawsuit, the Civil Court of Peace is responsible for hearing all disputes, including claims arising from rental relationships, concerning leased immovables and the lawsuits filed against such claims.
As a rule, the rent adjustment lawsuit is filed at the defendant's place of residence or where the real estate is located, i.e., where the contract is to be fulfilled.
4. DIFFERENCES BETWEEN RENT DETERMINATION AND RENT ADJUSTMENT LAWSUITS
In conclusion, if the conditions that influenced the parties to enter into a contract have significantly changed, the parties are no longer bound by the agreement. In such cases, it is possible to renegotiate the contract based on the changed circumstances. However, since adherence to the contract is fundamental, adjustment should always be considered as an auxiliary solution. 
1 Kılıçoğlu, Mustafa. Eviction Determination Adjustment Compensation and Debt Lawsuits. Ankara: Bilge Yayınevi, 2015.
2 Yargıtay 13th Civil Chamber – 6791/9014 24.10.1994 T.
3 Gümüş, Mustafa Alper. Lease Agreement. Istanbul: Vedat Kitapçılık, 2012.
4 Yargıtay 13th Civil Chamber – 13557/2495 10.03.2003 T.
5 YHGK 13-852/864 30.10.2002
6 Baysal, s,171
7 Gümüş, Mustafa Alper. Lease Agreement. Istanbul: Vedat Kitapçılık, 2012.
8 Kılıçoğlu, Mustafa. Eviction Determination Adjustment Compensation and Debt Lawsuits. Ankara: Bilge Yayınevi, 2015.