Public procurement contract amendment: room for maneuver under Kbt. 141. §, de minimis, unforeseeability

When can a public procurement contract be amended?

A contract concluded as the outcome of a public procurement procedure may be amended after the fact only if the amendment satisfies the conditions of one of the legal-ground subsections of Kbt. 141. §. Section 141. § contains three such subsections: paragraph (2) covers the value-based de minimis amendment, paragraph (4) covers amendments justified by specified circumstances across three sub-points, and paragraph (6) covers the test-based category of non-material amendments.

The current Kbt. consolidated within Kbt. 141. § the amendment rules that had been scattered across Act CVIII of 2011. The first comprehensive doctrinal treatment of this regime is the 2018 DJM study by Tarkó Izabel Ágnes. An amendment made outside these legal grounds qualifies as a contract concluded without conducting a new public procurement procedure.

How should the legal ground for the amendment be selected?

The choice of legal ground breaks down into five decision questions. The first concerns the coverage provided by an internal clause of the contract, followed in sequence by supplementary performance, an unforeseeable circumstance, the de minimis value cap, and finally the test for non-material amendment.

1. 01

   Amendment clauses

   Does an existing review clause or option right in the original contract cover the amendment request? If so, the legal ground is Kbt. 141. § (4) a). Documentation: the text of the clause and evidence that the triggering conditions have arisen. This covers price-review provisions, indexation clauses included.

   Kbt. 141. § (4) a)

2. 02

   Supplementary performance

   Supplementary works, services or supplies that cannot be separated from the main contract on economic or technical grounds without significant harm to interests? If so, the legal ground is Kbt. 141. § (4) b). Documentation: technical and economic justification, evidence of inseparability, and a value calculation against the 50% individual and cumulative cap.

   Kbt. 141. § (4) b)

3. 03

   Unforeseeable circumstance

   A circumstance that the contracting authority, acting with due diligence, could not have foreseen? If so, the legal ground is Kbt. 141. § (4) c). Documentation: identification of the circumstance, a timestamp, evidence of due diligence, a value calculation against the 50% cap, and a demonstration that the general nature of the contract remains unchanged.

   Kbt. 141. § (4) c)

4. 04

   De minimis value cap

   The value of the amendment stays below the EU procurement value threshold, remains below 10% of the original contract value for supplies and services or 15% for works and works or services concessions, and the general nature of the contract is not changed. Documentation: joint evidence of the EU threshold and the percentage cap, plus a running record of cumulative amendments.

   Kbt. 141. § (2)

5. 05

   Non-material amendment test

   The amendment would not have led to the participation of other tenderers or to a different winning tender, it does not shift the economic balance of the contract in favour of the winner, and it does not extend the contract to a new element. If any of these three cumulative conditions fails, Kbt. 141. § cannot be applied and a new public procurement procedure must be conducted. Ultimately, the Public Procurement Arbitration Board (KDB) may assess the lawfulness of the amendment.

   Kbt. 141. § (6) Risk of switching legal grounds

KDB practice calls out any amendment file that switches legal grounds mid-course, as Várhomoki-Molnár Márta's 12-part Jogászvilág series also walks through. The primary and the secondary reference subsections of Kbt. 141. § should already be fixed at the point the amendment request is formulated.

How do the three legal grounds differ from one another?

The three legal grounds are substantively alternative, but the parties cannot choose freely between them. What matters is a joint assessment of the caps across grounds: the values of de minimis amendments and of amendments based on specified circumstances aggregate, and the grounds are not interchangeable switches to be turned on and off at will.

The logic of the regime

The three legal grounds are substantively alternative, but the decision sequence and the cumulative value caps produce a practical constraint.

Comparison of the three principal legal-ground subsections of Kbt. 141. §

Legal ground	Condition	Value cap	Documentation	Aggregation
141. § (2) de minimis	The change in value stays below the EU procurement value threshold. The general nature of the contract is not changed.	Below 10% of the original contract value for supplies and services, 15% for works and works or services concessions.	Running record of aggregated value changes, EU threshold check.	Yes, within the same contract the values of successive de minimis steps add up.
141. § (4) a) review clause or option right	The original contract contains a clear, precise and unambiguous review clause or option, including provisions for price review.	No standalone percentage cap, the text of the clause sets the limit.	The text of the clause and evidence that the triggering conditions have arisen.	The clause may itself set the rule for repeated application.
141. § (4) b) supplementary works, services or supplies	The supplementary performance was not part of the original contract and cannot be separated from the main contract on economic or technical grounds without significant harm to interests.	The increase in consideration, individually and in aggregate, does not exceed 50% of the original contract value.	Technical and economic justification of inseparability, value calculation.	Yes, the values of amendments under 141. § (4) b) and c) both count towards the 50% cap.
141. § (4) c) unforeseeable circumstance	The amendment was made necessary by a circumstance that the contracting authority, acting with due diligence, could not have foreseen. The general nature of the contract is not changed.	The increase in consideration does not exceed 50% of the original contract value.	Identification of the circumstance, timestamp, evidence of due diligence, demonstration that the general nature of the contract remains unchanged.	Yes, the values of amendments under (4) b) and c) aggregate.
141. § (6) non-material amendment	Would not have led to the participation of other tenderers or to a different winning tender, does not shift the economic balance of the contract in favour of the winner, does not extend the contract to a new element.	No standalone percentage cap, test-based category.	Presentation of the three cumulative conditions in the amendment file.	Not a value-based category, aggregation is not meaningful here.

What does the 10-15% de minimis threshold apply to?

The 10% and 15% in Kbt. 141. § (2) are calculated against the original contract value, not against the remaining performance and not against a single amendment episode. The most common error is a miscalibration of the threshold. If the same contract has already seen an 8% de minimis amendment, the next de minimis step is limited to just 2% within the cap.

For works and for works or services concessions, the de minimis threshold is 15%. For supplies and services it is 10%, under Kbt. 141. § (2). The threshold applies only if the change in value stays below the EU procurement value threshold and does not change the general nature of the contract.

Why the 10-15% is not a free zone

The de minimis rule is available not only up to the percentage cap but also only where the change in value stays below the EU procurement value threshold. This ceiling routinely drops out of the reckoning in works contracts, where 15% is already a large amount in absolute terms. The KH guidance treats the unchanged general nature of the contract and the EU threshold ceiling as conditions to be read together with the percentage cap.

A common reading in practice treats 10-15% as a free zone. That is a simplification and it is misleading: the percentage cap protects only when three conditions are met together, and any professionally defensible amendment file has to demonstrate each of the three conditions independently.

On the specifics of municipal procurement, including the prohibition on splitting contracts, see our separate article on municipal public procurement.

What is the practical test for unforeseeability?

Kbt. 141. § (4) c) has been applied under a stricter test in recent years. In KH contract-review practice, the typical patterns of amendments that fall foul of Kbt. 141. § (4) and (6) are undocumented unforeseeability, an overly broad reading of the review clause, and extensions of the performance deadline outside the framework of Kbt. 141. §.

The argument fails systemically whenever the contracting authority did not record, at the time the circumstance arose, why it could not have been foreseen. The Arbitration Board no longer accepts a purely retrospective justification. It reviews the due-diligence test on a retrospective basis and requires the risk analysis to have covered the circumstance that materialized, or its type, already at the time the contract was concluded.

The practical takeaway: attach a one-page risk table to the internal file already when the procurement documents are being drawn up. The table records which circumstances fall into the unforeseeable category and which circumstances are covered by the review clause.

Szárnyasi János's large-sample series provides the system-level analysis of KDB practice, mapping which arguments hold up under which Kbt. 141. § legal ground. On the contracting-authority side, continuous monitoring of Arbitration Board case law is not optional. Without it, the legality assessment of any given amendment request is blind.

How can the winning tenderer initiate an amendment?

The winning tenderer may notify the contracting authority of an amendment request in writing. No statute requires the contracting authority to accept the amendment. Established professional practice, based on the duty of cooperation under the Ptk. (Civil Code), is that the request is considered on the merits and answered in writing.

Tenderer-initiated contract amendment receives limited coverage in the Hungarian public procurement literature, but in practice the winning tenderer is forced into it in many situations: an official permit is delayed, a subcontractor drops out, the financing is restructured. The initiative holds up when the winner flags the change in circumstances promptly and in documented form and drafts an amendment proposal that anchors itself explicitly to one of the specific subsections of Kbt. 141. §.

Restructuring the financing as a material amendment

According to the April 2025 case review in KÉ+, restructuring the financing of a contract qualifies as a material amendment. It fits neither the Kbt. 141. § (2) de minimis category nor the Kbt. 141. § (6) non-material amendment category. Amendment requests such as taking over the advance payment or restructuring the payment terms rarely succeed for the winner under Kbt. 141. § (2) or (6). The correct approach is either to build on Kbt. 141. § (4) a) clause coverage or to accept that the situation calls for a new public procurement procedure.

1. 01

   Notification

   The winner notifies the contracting authority of the change in circumstances in writing, dated, within a period close to the date on which the change occurred. A late notification weakens the argument of unforeseeability.

2. 02

   Documentation

   Attach the documents that evidence the change in circumstances: the official decision, the notification received from a third party, the reference to the legislation.

3. 03

   Choice of legal ground

   The written proposal names which subsection of Kbt. 141. § the amendment falls under, and the content of the proposal is aligned to that ground.

4. 04

   Remedy

   If the contracting authority rejects the request or does not answer on the merits, the winner may turn to the Public Procurement Arbitration Board with an application for review. A rejection is not always final: the winner may first ask for a written statement of reasons.

When must the contract amendment be published?

The notice on the contract amendment must be published in the Public Procurement Bulletin within 15 working days from the amendment of the contract at the latest. The contract amendment carries a standalone publication obligation and should be read together with the formal rules on notice submission.

The most common slip in meeting the 15 working-day deadline comes from miscounting the days from the amendment. Some contracting authorities are thrown off by starting the count from the signature of the amendment rather than from the point at which the agreement between the parties was reached. The other typical slip is that several amendment episodes appear in a single notice, weeks after the first episode.

The contract-amendment sub-section of the Public Procurement Authority's Primer consists of four skeletal sub-pages, typically with one-to-two-sentence definitions and outbound links. The practical depth is provided by the 7 October 2025 KH guidance and by the Simon Enikő KÉ+ article.

Typical focus areas of KH contract review (Simon Enikő 2024)

Four focus areas recur in KH contract-review practice:

• Undocumented unforeseeability
• Overly broad reading of the review clause
• Deadline extensions outside the framework of Kbt. 141. §
• Switching legal grounds within the amendment file

If you need advisory support to prepare your own contract-amendment notice, we handle it as an administrative deliverable within Sugallat's public procurement advisory service for contracting authorities.

What are the legal consequences of an unlawful amendment?

An amendment in breach of Kbt. 141. § is null and void. Under Kbt. 137. § (1) a), a contract is null and void if it was concluded by unlawfully bypassing the public procurement procedure, and an amendment in breach of Kbt. 141. § qualifies as a contract concluded without conducting a new public procurement procedure.

The line between this and an unlawful bypass of the public procurement procedure matters for exposure to fines and for the burden of proof. Pfeffer Zsolt PhD's 2021 KÉ+ study works through this distinction. In an unlawful bypass, no fine is imposed on the economic operator. In an unlawful amendment, both parties are exposed to a fine under the Kbt.'s sanctions regime.

Unlawful bypass of the public procurement procedure

The contract is concluded from the outset without any public procurement procedure being conducted, even though the Kbt. required one. The subject of proof is the material scope of the Kbt. and the value calculation against the threshold.

Unlawful contract amendment

The contract was concluded on the basis of a public procurement procedure, but a later amendment was made that does not fall under any single subsection of Kbt. 141. §. The subject of proof is the tension between the amendment and the legal-ground caps of Kbt. 141. §.

In a European comparison, Hungarian law has chosen the narrower of the available sanction models. According to Ferge Péter's 2023 KÉ+ study, the EU-law consequence may also be rescission or termination, and nullity is not the only available sanction model. Hungarian law chose the nullity route: the contract is invalid from the date of the amendment, and the parties are required to settle with each other under the invalidity rules of the Ptk.

Unsure which Kbt. 141. § legal ground a specific amendment scenario falls under?

For any given amendment request, the choice of legal ground, the documentation and the publication timetable are rarely obvious. Let us review the situation with you and tell you what to do next.

Ask the expert

What are the risks of amending a grant-funded contract?

Amending a public procurement contract financed from EU funds sits at the intersection of two review frameworks. The first is public procurement legality under Kbt. 141. §, which the Public Procurement Authority reviews at the contract-review stage. The second is compliance with the eligibility rules of the grant agreement and the call for proposals.

Compliance on eligibility is reviewed by the Public Procurement Supervisory Department of the Prime Minister's Office (KFF) as ex ante control, and, where relevant, by the managing authority under an irregularity procedure. Legality under the Kbt. does not preclude a finding of irregularity on the project-supervision side.

Grant recovery combined with the nullity of the unlawful amendment is financially the most drastic outcome. Under the invalidity settlement rules of the Ptk., the parties return the services to each other and, where that is not possible, provide compensation in cash. In the case of construction work already carried out, this value refund also reshapes the funding side of the grant-supported budget, and the recovery ordered in the irregularity procedure can add to the total financial exposure.

How should indexation be applied?

An indexation provision (in professional usage, a price-adjustment provision) is a price review clause under Kbt. 141. § (4) a). The legal ground for indexation built into a public procurement contract is therefore neither de minimis nor unforeseeability but the original contract itself.

An indexation provision cannot be inserted into the contract retrospectively, only within a specific, quantifiable amendment based on another subsection of Kbt. 141. §. The contracting authority sets the clause in the procurement documents and the winner accepts it with the tender.

The 7 October 2025 KH guidance goes substantively further than earlier versions in three areas: indexation formulas with worked examples (based on KSH data), a detailed treatment of additional works under Kbt. 141. § (4) b) and c), and a treatment of the amendment rules for framework agreements (Kbt. 105-107. §) and framework contracts (Kbt. 108. §). The amendment rules for framework constructions run under distinct conditions even within the framework of Kbt. 141. §. The retroactive effect of KH guidance is limited. The guidance applies to contracts concluded in new procedures launched after it enters into force and does not extend to matters already under way.

1. 01

   Base period

   The period whose price level is used as the reference for indexation. Typically the month, quarter or year of contract conclusion.

2. 02

   KSH index selection

   The KSH data series that fits the contract type. For works, the construction producer price index. For energy supply, the energy price index. For general services, the consumer price index or one of its sub-categories may apply. The source is the official KSH table system.

3. 03

   Indexation formula

   New price = original price multiplied by (current KSH index value divided by base-period KSH index value). Example: if the original price is 100 units, the base-period KSH index is 100 and the current KSH index is 108, the new price is 108 units, that is an 8% indexation uplift.

4. 04

   Minimum and maximum thresholds

   The indexation provision may set indexation to apply only where a minimum threshold (e.g. a 3% KSH change) is crossed, and to require separate negotiation above a maximum threshold (e.g. 20%). The threshold system protects both parties from extreme KSH movements.

5. 05

   Frequency of application

   Indexation may be applied annually, semi-annually, quarterly or on a contract-event basis (e.g. a partial-performance milestone). The guidance says the frequency should be tailored to the nature of the contract.

Additional works or supplementary works?

Additional works are a public procurement contract-amendment case, falling under Kbt. 141. § (4) b) or c). Supplementary works, by contrast, are part of the technical content of the contract and are settled under the Ptk. and the contract remuneration rules. The distinction is routinely mishandled in works contracts.

Construction case law and doctrinal literature work through this distinction within the Ptk. and Kbt. framework, together with the case-law references. From the construction side, the MeRSZ Építési közbeszerzés (Construction Public Procurement) textbook, chapter IX.3, provides the textbook-style summary (paid professional source).

Additional works

Work that was not foreseeable at the time of contract conclusion or was not part of the technical content, and that becomes necessary afterwards for the delivery of the contract result. A public procurement contract-amendment case falling under Kbt. 141. § (4) b) or c). Any change in consideration requires public procurement documentation (legal ground, necessity, inseparability or unforeseeability), and it carries a standalone publication obligation under the 15 working-day rule.

Supplementary works

Work that is part of the technical content of the contract or can be clearly derived from it, but whose quantity in actual delivery exceeds the contractual (design) quantity. A matter of contractual consideration, settled under the Ptk. and the remuneration rules of the contract. Not a public procurement contract amendment, so Kbt. 141. § does not apply and no standalone contract-amendment notice is required.

The most common error is that the contractor reports as additional works items that are in fact supplementary works (a quantity divergence from the contractual design), or the other way around. Among practical Q&A sources, the additional-works keyword index of Közbeszerzési Levelek lists several dozen expert answers, which is a signal that this is one of the most frequently raised sub-topics in the professional Q&A sources (paid professional database).

When can a public procurement contract be amended under Kbt. 141. §?

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What is the de minimis value threshold, and do successive amendments aggregate?

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When is a public procurement contract amendment null and void?

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By when must the notice of a contract amendment be published?

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