In construction and other contracts for work, the parties generally determine the scope of work, technical specifications and contract price at the beginning of the project. In practice, however, employers frequently request new work after construction has begun, revise the original project or require the contractor to perform work that was not contemplated when the contract was signed.
This raises an important question: Can a contractor claim additional payment for work performed after the original contract was concluded?
As a general principle, a contractor may be entitled to additional payment for work that genuinely falls outside the original contractual scope. However, not every increase in cost or quantity automatically creates a separate payment claim.
Does a Lump-Sum Price Cover Every Subsequent Work?
Article 480 of the Turkish Code of Obligations (“TCO”) provides that where the contract price has been agreed on a lump-sum basis, the contractor must complete the agreed work for that price. The fact that performance requires more labour or expense than expected does not, by itself, give the contractor a right to request a price increase.
A distinction must therefore be made between two situations.
The first concerns work already included in the contractor’s original scope that turns out to be more expensive or difficult than expected. Additional labour required for the same construction item or an increase in the contractor’s costs does not, as a rule, constitute “additional work.”
The second concerns new work or construction items that were not included in the original contractual scope but were subsequently required from the contractor. In that situation, the lump-sum price does not automatically cover the new work outside the contract.
In a decision dated 22 October 2025, the 6th Civil Chamber of the Court of Cassation upheld a decision in which the value of additional work arising from construction quantity increases outside the lump-sum scope had been calculated using local market prices for the year in which the work was performed. The underlying dispute arose from a subcontract. The decision does not mean that every quantity increase automatically qualifies as additional work; the work must first be shown to fall outside the contractual scope. (Court of Cassation, 6th Civil Chamber, E. 2025/3147, K. 2025/3517, 22 October 2025)
What May Qualify as “Additional Work”?
Calling an item an “extra” is not sufficient on its own. The contract, technical specifications, drawings, bills of quantities, schedules and other contractual documents must first be examined.
Examples of work that may potentially give rise to a separate payment claim include:
- a new construction item requested by the employer but not included in the contract;
- additional construction required as a result of a subsequent design change;
- additional sections or work added to the project by the employer; and
- additional installations, structures or applications not contemplated in the original contractual documents.
By contrast, work that the contractor was already required to perform in order to achieve the result promised under the contract does not become additional work merely because it costs more than expected.
Accordingly, one of the first steps in an additional-work dispute is to technically distinguish the original contractual scope from the work performed afterwards.
Is a Written Instruction from the Employer Required?
The strongest evidence of additional work is generally a written instruction from the employer or a supplemental agreement signed by the parties. However, the absence of a separate written agreement does not necessarily mean that the claim must be rejected.
In a decision dated 26 December 2022, the 6th Civil Chamber of the Court of Cassation held that evidence showing that additional work had been performed by the contractor and physically taken over should be assessed even though there was no separate written agreement for that work. The dispute concerned construction work for a university and therefore arose in a public-sector setting; its public-construction regime should not be applied wholesale to private-sector contracts. The decision is relevant here for the narrower point that the absence of a written supplemental agreement does not, by itself, end the inquiry. (Court of Cassation, 6th Civil Chamber, E. 2021/5038, K. 2022/6074, 26 December 2022)
In commercial disputes in particular, contractual requirements for written changes, notice and approval, as well as the evidentiary rules under the Code of Civil Procedure, may significantly affect the outcome.
Contractors should therefore preserve evidence such as emails and messages from the employer, revised drawings, site records, progress-payment documents, quantity measurements, work schedules, photographs, invoices and delivery records.
How Is the Price of Additional Work Calculated?
If the parties have agreed on the price of the additional work or on a method for calculating it, that agreement should be considered first.
Where there is no such agreement, the provisions of the TCO concerning contracts for work and, depending on the circumstances, management of affairs without mandate may become relevant.
Under Article 481 TCO, where the price of a work has not been fixed in advance or has only been determined approximately, the price is established by reference to the value of the work at the place and time of performance and the contractor’s expenses.
In cases concerning work outside the contract, the Court of Cassation has relied on local market prices applicable when the work was performed, depending on the circumstances. For example, in a decision dated 17 February 2026, the 6th Civil Chamber upheld an award for contract-external work that was eligible for payment, valued using free-market prices applicable when it was performed. The underlying case concerned a public construction contract and the General Conditions for Construction Works; those public-procurement rules do not directly govern private-sector contracts. (Court of Cassation, 6th Civil Chamber, E. 2025/2628, K. 2026/577, 17 February 2026)
The Court of Cassation has also stated that, where local market prices are treated as already including contractor profit and VAT, those elements should not be added a second time. (Court of Cassation, 6th Civil Chamber, E. 2021/5038, K. 2022/6074, 26 December 2022)
Can a Contractor Claim for Every Improvement Made on Its Own Initiative?
No.
A contractor does not automatically acquire a right to additional payment simply because it voluntarily used higher-quality materials or improved the project beyond the contractual requirements.
In particular, additional payment may not be available for improvements made without the employer’s request where the work also benefits the contractor itself.
The Court of Cassation has held that the employer’s benefit, the work’s economic value and the circumstances of the case must be considered in determining whether the contractor may claim separately for work outside the contract. Additional payment may not be recoverable for improvements that also benefit the contractor’s own units or otherwise serve both parties’ interests. (Court of Cassation, 23rd Civil Chamber, E. 2012/5334, K. 2013/2017, 29 March 2013)
Accordingly, the argument that “the work was not mentioned in the contract, so I am entitled to payment” is not sufficient by itself.
Evidence Is Often the Decisive Issue
In additional-work disputes, the main difficulty is often not the legal remedy itself but proving which work was included in the original contract and which work was added later.
As far as possible, a contractor should retain:
- the original contract and drawings;
- subsequent design revisions;
- the employer’s instructions concerning additional work;
- quantity and measurement records for the additional work;
- photographs and records showing that the work was performed;
- evidence of delivery or use by the employer; and
- any quotations or price proposals submitted for the additional work.
Where the dispute reaches court, technical expert evidence is frequently required to determine which construction items fell within the original scope, which were additional, and the market value of that additional work at the relevant time.
Conclusion
The existence of a lump-sum construction contract does not mean that a contractor must perform every work subsequently requested by the employer for the original contract price.
Where additional construction is carried out following an employer’s request or a project change and genuinely falls outside the original contractual scope, the contractor may be entitled to claim additional payment.
The success of such a claim will usually depend on three central issues: proving that the work fell outside the original contract, proving that it was actually performed for the employer, and applying the correct method for determining its value.
For that reason, particularly in construction projects where the scope frequently changes during performance, recording additional-work instructions and quantities in writing when they arise can substantially reduce later disputes over payment.
This article is provided for general informational purposes under Turkish law. It does not constitute legal advice or an opinion on any particular matter.