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Unjust enrichment on a construction site — payment for additional works without an annex (Articles 405 and 410 of the Polish Civil Code)

Ten artykuł jest dostępny także po polsku. Dieser Beitrag ist auch auf Deutsch verfügbar.

The contractor performed works that were not in the design. No annex was signed, because „the lump sum covers everything”. The employer took over the structure and uses it — but does not intend to pay. Polish case law answers such situations with the provisions on unjust enrichment (Articles 405 and 410 of the Civil Code). This route genuinely works, yet it hides a trap which losing parties discover too late, it splits the courts of appeal into diverging lines, and it has several limits worth knowing before filing suit. Below is the whole map: the legal bases, three readings of the same provision, the evidence, the value of recovery, limitation and the arguments of both sides.

Where the problem comes from

Lump-sum remuneration prices the performance described in the contract and its documentation. When it turns out mid-construction that works not provided for in the documentation are needed to hand over a functioning structure, the contractor faces a choice: stop the site and demand an annex, or perform the works and hope to settle later. The employer usually has no interest in signing any annex — we describe the mechanics of that blockade in the article on judicial increase of a lump-sum price. Since the contract was never amended and the works were done, what remains is settlement outside the contract. That path is unjust enrichment. Where exactly the boundary between works covered by the lump sum and works beyond it runs, we explain in the analysis of the scope of lump-sum remuneration — here we assume the works genuinely went beyond the contract.

The legal basis: Articles 405 and 410 of the Civil Code

The general rule reads: „Whoever without a legal basis has obtained a financial benefit at the expense of another person is obliged to return the benefit in kind, and if that is not possible, to reimburse its value” (Article 405 of the Civil Code, consolidated text: Dz.U. 2024 item 1061). Its particular form is undue performance — Article 410 § 2 covers, among other situations, the one in which the legal act obliging the party to perform „was invalid and did not become valid after the performance was rendered”. On a construction site this corresponds to two settings, which are worth distinguishing from the outset because they differ in the burden of proof.

How the case law opened this route

The foundation was laid by the Supreme Court judgment of 7 November 2007, II CSK 344/07 (LEX No. 388844), whose holding the Court later summarised as follows:

„[W]here the invalidity of the contract, on account of non-compliance with the required form, precludes awarding that equivalent as remuneration, there is no obstacle to taking the equivalent value of those works into account under the provisions on unjust enrichment, since the defendant was indisputably enriched by their value.”

— judgment of the Supreme Court of 2 February 2011, II CSK 414/10, LEX No. 738545, citing the holding of the judgment of 7 November 2007, II CSK 344/07

The line is continued by the judgments of 21 May 2009, V CSK 439/08 (LEX No. 518121) and of 25 June 2010, I CSK 544/09, and in the realities of public procurement by the judgment of 7 February 2013, II CSK 248/12 (LEX No. 1293945), where the Supreme Court accepted the classification in plain words: „a performance rendered in execution of an invalid contract must be qualified as an undue performance”. It also mattered there that the works had been carried out with the employer’s knowledge and consent, „albeit expressed in an improper form”, and that their need arose from causes attributable to the employer. The Supreme Court upheld this direction in the judgment of 11 May 2017, II CSK 541/16 (LEX No. 2329450). A more cautious tone has, however, appeared in newer case law — in the judgment of 8 March 2018, II CSK 325/17 (LEX No. 2497992), the Court distanced itself from treating the construction as automatic, of which more below.

Subcontractors — the same principle

The mechanism also works down the subcontracting chain. In the case closed by the Supreme Court judgment of 28 August 2013, V CSK 362/12 (LEX No. 1391375), subcontractors had performed works under an oral contract, invalid for lack of the written form then required for subcontracts by Article 647¹ of the Civil Code. The Supreme Court recalled that it had already been explained in the case law that „a claim for the value of materials built into the employer’s building, or of labour, in performance of an invalid construction works contract is a claim for the value of an undue performance” — alongside II CSK 344/07 and IV CSK 460/07 it cited the judgments of 29 April 2005, V CK 537/04 (LEX No. 519298) and of 5 December 2006, II CSK 327/06. Mind the current state of the law: since 1 June 2017 the subcontract itself no longer requires written form on pain of invalidity — that sanction now attaches to the notification of the subcontractor to the investor and to the investor’s objection (Article 647¹ § 4) and to the investor–contractor agreement identifying the subcontractor (Article 647¹ § 2). The enrichment route remains fully relevant wherever invalidity follows from other causes, for instance lack of authority of the signatory.

The 720 chases case — the 2014 breakthrough

The most important judgment of this line remains the Supreme Court judgment of 9 October 2014, I CSK 568/13 (LEX No. 1541043). A subcontractor was to install sanitary systems in 127 apartments for a lump sum of PLN 2,725,620 net, following a design imposed on it. During the works the specified pipe system ceased to be available from the manufacturer, so with both parties’ consent a different, more expensive system was used — dearer by PLN 119,952 net in the cold-water part. In addition, on the site inspector’s instruction the subcontractor cut 720 chases for cabling which the detailed design did not provide for and without which, as the courts established, the contract could not have been performed.

„The construction of lump-sum remuneration — as is also emphasised in the literature — does not therefore exclude a claim by the contractor for remuneration for works not covered by the contract.”

— judgment of the Supreme Court of 9 October 2014, I CSK 568/13, LEX No. 1541043

The theoretical weight of the judgment lies in a sentence which appears earlier, when the Court discusses the principle that a lump sum is immutable:

„In connection with the principle of immutability characterising lump-sum remuneration, both legal writing and the case law point out that this remuneration constitutes the equivalent for the execution of a designated work. The agreed amount relates to the scope of performance established by the parties.”

— judgment of the Supreme Court of 9 October 2014, I CSK 568/13, LEX No. 1541043

In other words: the immutability of the price concerns the performance described in the contract, not everything that may ever prove necessary for the aim of the investment. That reverses the perspective used by part of the judiciary („since the works were necessary, they were covered by the lump sum”). The objection of lack of professional diligence (Article 355 § 2 of the Civil Code) failed, because the contractor had no design qualifications in the sanitary trade and could not have caught the defects of someone else’s design.

One provision, three outcomes — how courts read „works not covered by the contract”

The key to winning or losing lies in what a given panel understands by „works not covered by the contract”. Three readings function in parallel in the courts of appeal, and it pays to know all three, because the defendant will quote the first and the claimant the third.

The strict reading: whatever is necessary is in the price

An example is the judgment of the Court of Appeal in Kraków of 11 September 2015, I ACa 715/15 (LEX No. 1927533). The contractor of a school sports hall (lump sum of PLN 5,060,589 gross) claimed payment for works confirmed in necessity protocols: a central-heating connection (PLN 21,328.90), the levelling of differences between the buildings (PLN 11,805.54) and the adaptation of a power connection designed contrary to the technical conditions (PLN 19,845.53). The regional court awarded a total of PLN 52,979.97 as unjust enrichment. The court of appeal varied the judgment and dismissed those claims:

„The fact that, with respect to these categories of works, the design assumptions were defective or incomplete remains irrelevant for the assessment expressed here, since such a situation is covered by the contractor’s risk resulting from its consent to fixing the remuneration as a general amount, in principle immutable […]”

— judgment of the Court of Appeal in Kraków of 11 September 2015, I ACa 715/15, LEX No. 1927533

The court reasoned that since the subject of the contract had been described comprehensively (construction of the hall „together with the external infrastructure”), a professional had to price those works in as well, even though the design assumptions proved defective. The same judgment carries a second warning: the necessity protocols had been signed by trade site inspectors, not by persons authorised to represent the employer — so no separate contracts for those works came into being. Finally, the Kraków measure of enrichment deserves a note as an isolated position: in that panel’s view the size of the enrichment „expresses the extent to which their value exceeds the global sum fixed as the lump sum for the performance of the subject of the contract” — enrichment would only be the surplus of the value of all works over the entire lump sum, which on large contracts practically kills the claim.

The middle reading: the limit of foreseeability

The Court of Appeal in Gdańsk, in the judgment of 12 March 2014, V ACa 846/13 (LEX No. 1488615), adopted a two-step formula. A lump sum excludes payment for additional works which „are a natural consequence of the construction process and follow from it in a natural way”, and also for those which a contractor holding the documentation „should foresee as necessary to perform even though the documentation does not provide for them”. It is not justified, however, to expect the exclusion to reach further: where the documentation on which the price was calculated contains errors preventing achievement of the result, payment for works caused by those errors is not ruled out. That case concerned a defectively designed route of sanitary and rainwater sewage which could not have been detected before the works began.

The favourable reading: the lump sum prices the described performance

This is the I CSK 568/13 line discussed above — the price is assigned to the performance specified in the contract and its documentation, so works not included there are „not covered by the contract” even if they were necessary. In practice, what decides between the three readings is the quality of the comparative material: the more precisely the works actually performed can be set against what the documentation described, the less room remains for the formula „everything was necessary, so everything was in the price”. We describe the method of that comparison in the article on the scope of the lump sum.

The trap you must know: Article 411(1) of the Civil Code

This is the most frequently overlooked obstacle in additional-works cases. The Code provides:

„Return of a performance cannot be demanded: 1) if the performing party knew that it was not obliged to perform, unless the performance was rendered with a reservation of return, or in order to avoid coercion, or in execution of an invalid legal act […]”

— Article 411 of the Civil Code

Note the paradox. The whole construction rests on the premise that the additional works were not covered by the contract — which means the contractor knew it did not have to perform them, and performed them anyway, usually without any reservation. Read literally, the provision would then exclude recovery. The case law has worked out three exits, and each of them translates directly into how a site should be run.

Exit one: the reservation of return

The simplest and cheapest. When starting the disputed works, the contractor declares in writing that it performs them with a reservation of the return of their value, because it considers them outside the contract. One sentence in a letter delivered to the employer closes this entire line of defence. That this is not just theory is shown by the Supreme Court judgment of 15 May 2014, II CSK 517/13 (LEX No. 1488794), decided outside construction: a franchisee kept paying inflated fuel prices, but in its letters demanding correction of the invoices it reserved the return — and precisely for that reason Article 411(1) did not bar recovery of the overpayments. On a construction site such a reservation can be a covering letter to a necessity protocol or a clause in the correspondence announcing commencement of the disputed works. In practice almost nobody does it.

Exit two: economic coercion

The most important one in practice. The notion of coercion in Article 411(1) is not interpreted narrowly — beside classic enforcement coercion (as with a performance collected by a bailiff: Supreme Court judgment of 9 August 2012, V CSK 372/11, LEX No. 1231631) it covers acting to avoid severe economic consequences. The contractor usually must perform the unforeseen works, because without them it cannot complete the contractual works — and stopping the site until an annex is signed would expose it to delay, contractual penalties (Article 483 § 1 of the Civil Code) and damages liability (Article 477 § 1), not rarely also to the employer’s termination. The Court of Appeal in Białystok put it exactly this way in a case concerning the recultivation of a municipal landfill, where the contractor had to move far greater masses of waste than the design assumed (among others 10,580 m³), while the contract allowed additional works to be settled only through a necessity protocol and a free-hand supplementary order, which the employer never initiated:

„Despite being aware that it was performing unduly (without a necessity protocol and an additional order), the claimant had to perform the scope of works increased in comparison with the contractual one, as indispensable for completing the works covered by the contract and achieving the aim of the contract. Otherwise it could not have continued the successive stages of the works covered by the contract (and would in addition have exposed itself to a possible charge of untimely contractual performance and to liability under the contractual penalties stipulated in the contract).”

— judgment of the Court of Appeal in Białystok of 23 June 2017, I ACa 69/17, LEX No. 2327817

That case was decided on the background of cost-estimate remuneration, but the mechanism of Article 411(1) works identically with a lump sum. At Supreme Court level this direction is expressed by the judgment of 11 May 2017, II CSK 541/16 (LEX No. 2329450). The boundary is set by the standard of awareness — exclusion of recovery requires full and positive knowledge, doubts are not enough:

„As the Supreme Court indicated in the judgments of 12 December 1997 (III CKN 236/97, OSNC 1998, No. 6, item 101) and of 10 June 2003 (I CKN 390/01, OSP 2005, book 9, item 111), doubts as to the obligation to render a performance cannot be equated with the positive knowledge of the debtor, required by Article 411(1) of the Civil Code, that there is no duty to perform.”

— judgment of the Court of Appeal in Gdańsk of 5 September 2016, I ACa 1168/15, LEX No. 2166478

In a dispute over the limits of a lump sum the contractor almost always has doubts — and that is what protects it. The assessment may be different where the contractor acted entirely outside any procedure, without notification and without any signal to the employer, in full awareness that it had no obligation.

Exit three: performance of an invalid legal act

This concerns the second setting — an agreement tainted by invalidity. The same Gdańsk judgment puts it directly:

„Return of a performance can also be demanded where it was rendered in execution of an invalid legal act. In that case the return takes place irrespective of the performing party’s knowledge of the duty to perform.”

— judgment of the Court of Appeal in Gdańsk of 5 September 2016, I ACa 1168/15, LEX No. 2166478

It is this gate that opens the road to claims in public procurement, where agreements lacking written form are invalid by force of Article 432 of the Public Procurement Law.

What must be proven — and under which condiction

The choice between Article 405 and Article 410 is not an academic subtlety but a difference in the burden of proof. For undue performance the case law accepts a substantial simplification:

„[F]or the claim defined in Article 410 of the Civil Code there is no need to establish anything else, including whether the performance enriched the recipient or whether the estate of the performing party was diminished, since these premises follow from the very concept of undue performance. The mere fact of rendering an undue performance justifies, in that case, the restitution claim […]”

— judgment of the Supreme Court of 28 August 2013, V CSK 362/12, LEX No. 1391375, following the judgments of 24 November 2011, I CSK 66/11, LEX No. 1133784 and of 9 August 2012, V CSK 372/11

So if the works were performed under an invalid agreement (the second setting), it suffices to prove the performance and its value. Under pure Article 405 (the first setting) all the premises must be proven: enrichment, impoverishment and the link between them — and courts treat them as equal in rank, so failure to prove any one of them means dismissal. That is how the case before the Court of Appeal in Szczecin ended (judgment of 14 March 2013, I ACa 877/12, LEX No. 1344241), where the claimant proved his own expenses but not the value by which the other party’s estate had grown. In a construction dispute the evidence list looks like this:

How much can realistically be recovered

What is returnable is the value of the benefit, not the contractual remuneration and not the sum of purchase invoices. The distinction is often neglected, and it cuts both ways. Because construction works cannot be returned in kind, their value must be reimbursed — established objectively, at market prices. The case law has settled a two-quantities rule here:

„[T]he value of unjust enrichment is limited by two quantities, namely the value of what left the estate of the impoverished party without a legal basis, and the value of what increased the estate of the enriched party without a legal basis. These values need not be equal, and in the case of inequality the lower amount determines the value of the unjust enrichment […]”

— judgment of the Court of Appeal in Szczecin of 14 March 2013, I ACa 877/12, LEX No. 1344241, invoking the Supreme Court judgments of 24 October 1974, II CR 542/74, OSPiKA 1976/6/115, of 17 April 2000, V CKN 32/00, LEX No. 52429 and of 19 March 2002, IV CKN 892/00, LEX No. 54380

Three practical consequences follow. First, a contractor who performed the works below market rates may claim the market value, not merely its own costs — in the Kraków hall case the expert confirmed that the contractor’s demand was lower than the rates commonly applied in the trade, which harmed no one. Secondly, the employer will argue that its benefit is lower than the contractor’s expenses — for instance because part of the works it would have had to procure differently anyway, or because the structure gained less in value than the works cost. Thirdly, it is disputed whether the contractor’s profit falls within the value of the return: part of the legal literature takes the view that profit is not a component of the employer’s benefit, so when calculating the demand it is safer to prove the market value of the performance (which carries the profit mark-up inside it) than to add profit as a separate item.

How sharply courts can trim a claim is shown by the municipal boiler-house modernisation case closed by the Supreme Court judgment of 11 March 2010, IV CSK 401/09 (unpublished): the contract proved invalid due to defective representation of the municipality, and of a demand of nearly PLN 500,000 the courts ultimately awarded PLN 218,158.12 — they excluded from the value of the enrichment, among other items, VAT and the contractor’s so-called general costs (calculated at PLN 209,957), and the court of appeal indicated that „the subject of the return should be the average market price of the services and equipment as at the date the return was demanded”. The claim does not cover lost profit in the compensatory sense either — if the additional works originate in errors of the design documentation, fuller compensation may be available through the damages route of Article 471 of the Civil Code, which however requires proof of a breach and of loss.

Why this claim is weak by nature: Article 409 of the Civil Code

This must be said to the client before litigation. The Code provides: „The obligation to return the benefit or to reimburse its value expires if the party which obtained the benefit has consumed it or lost it in such a way that it is no longer enriched, unless, when disposing of the benefit or consuming it, it should have reckoned with the obligation of return” (Article 409). With construction works the enrichment usually has the durable form of a structure, so the risk of expiry is limited — but not zero, especially where the employer has sold the property or the structure was rebuilt. The key is then to show that the enriched party should have reckoned with the obligation of return. In the boiler-house case the municipality defended itself precisely with the wear and tear of the equipment — unsuccessfully, because by allowing it to wear down in the course of the dispute it should have reckoned with the return. A contractor who raises its payment demands contemporaneously builds that proof for itself.

Limitation and interest — three rules people forget

A claim in unjust enrichment has no fixed date of performance, so it becomes due only upon a demand for payment (Article 455 of the Civil Code). From that moment default interest runs — in the Białystok case the court counted it from the deadline in the demand, not from the date the works were performed. But beware of limitation: its running does not wait for the demand. Under the second sentence of Article 120 § 1 of the Civil Code the period starts on the day the claim would have become due had the creditor called on the debtor at the earliest possible date — in practice, from the rendering of the performance. For a contractor running a business the period is three years and it ends with the last day of the calendar year (Article 118).

The third rule is the most valuable procedurally. In the boiler-house case the defendant municipality argued that since the statement of claim had been based on the (invalid) contract, it did not interrupt the limitation of the restitution claim until the claimant changed the action. The Supreme Court rejected that view:

„It follows from this provision that the unjustly enriched party becomes the debtor of the impoverished party by the mere fact of the unjust enrichment, and that upon the unjust obtaining of the benefit there arises on its side the obligation to return the benefit or to pay its value.”

— judgment of the Supreme Court of 11 March 2010, IV CSK 401/09, unpublished

A statement of claim covering the same payment demand, based on the same facts, interrupted the limitation period (Article 123 § 1 point 1 of the Civil Code) also for the claim under Articles 405 and 410 — no change of action within the meaning of Article 193 § 1 of the Code of Civil Procedure was needed.

The procedural trap: how to frame the claim

In the II CSK 344/07 case the claimants pursued the amount as remuneration for additional works, and the court of appeal — following the Supreme Court judgment of 18 March 2005, II CK 556/04 — held that Article 321 § 1 of the Code of Civil Procedure did not allow the sum to be awarded as unjust enrichment when a contractual performance had been demanded. The Supreme Court removed that obstacle: „the factual basis of the claim is the same, what is at stake is the return of the value of the outlays made. That is the subject of the demand within the meaning of Article 321 § 1 of the Code of Civil Procedure”. The line then solidified:

„[I]f the claimant demands that a specified sum of money be awarded on the basis of a contract concluded with the defendant, the court — having found that contract invalid — may allow the claim on the basis of the provisions on unjust enrichment, without any need for an objective change of the action.”

— so the Supreme Court in the judgment of 2 February 2011, II CSK 414/10, summarising the judgment of 11 March 2010 designated there as „IV CSK 401/10″ — in reality case No. IV CSK 401/09

Even so, caution dictates describing the full factual basis in the statement of claim — the works, their source, their value and the employer’s benefit — and indicating the legal bases in the alternative. It costs one paragraph and closes the defendant’s cheapest line of defence. The limit remains Article 321 § 1: the court will not go beyond the demand or beyond the factual basis, so the facts pleaded must cover both qualifications.

Weak points of the construction and the other side’s arguments

An honest assessment of the odds requires knowing the objections the employer will raise. Some of them carry real weight.

Really „without a legal basis”?

The most serious theoretical objection. If the contractor is answerable for the result, then works necessary to hand over a functioning structure fall within what it owes — they are merely not priced. A legal basis for performing them therefore exists in the contract itself, and only its counterpart on the remuneration side is missing. A simple test exposes the construction: if the works truly were „not covered by the contract”, the contractor could refuse to perform them — yet nobody grants it that right, everyone treats the works as owed within the liability for the result. Something owed under a contract is hard to treat, at the same time, as performed without a legal basis. From this standpoint, reaching for unjust enrichment is a prosthesis with which the case law fills a systemic gap — and it is this inconsistency that resurfaced in the more cautious tone of II CSK 325/17. In practice, however, the construction works and remains the most frequent real road to the money.

Imposed enrichment

The employer will say it never ordered the works and had no influence on the decision to perform them, and yet is charged with a cost it did not plan and sometimes cannot bear. The objection can succeed where the contractor acted on its own and without notification. It loses force where it is documented that the impulse came from the employer, the designer or the site inspector — which is why site-log entries, instructions and correspondence matter so much. In the Białystok case it was precisely the contractor’s entries and letters that settled that the municipality could not hide behind the absence of a formal order which it itself should have initiated.

The competence objection

The construction silently assumes the contractor was able to perform all works necessary to achieve the result. It happens otherwise — some works require qualifications or equipment the contractor does not have, as with specialist ground drilling. This is rather an argument for the contractor: if it could neither foresee them nor perform them with its own resources, it is all the harder to claim they fitted within its lump sum. That is exactly how the lack of design qualifications worked in the 720 chases case.

The risk of a defects charge

A trap few think about. A contractor which unilaterally departs from the solutions described in the contract — even so that the structure works at all — exposes itself to the charge of delivering a performance non-conforming with the contract. A defect consists precisely in the non-conformity of the thing with the contract (Article 556¹ § 1 of the Civil Code, applied to construction works via Articles 656 § 1 and 638 § 1), not merely in objective malfunction. Departures should therefore never be introduced quietly: first the notification under Article 651, then a demand for the employer’s decision, and only at the end the works.

An alternative worth remembering: a new agreement instead of condiction

Where the parties agreed on a substitute solution (as with the change of the pipe system in the 720 chases case), it can be argued that a contract for the substitute works was simply concluded — and if no price was agreed, the ordinary remuneration determined by analogous application of Article 628 § 1 of the Civil Code comes into play. This route bypasses the whole problem of Article 411(1), but requires proof of consensus on the scope. Outside public procurement it tends to be underrated.

Design and build — where the construction fails

Contracts in which the contractor also took over the design form a separate category. In the case closed by the judgment of the Court of Appeal in Katowice of 29 January 2014, I ACa 821/13 (LEX No. 1441387), the design-and-build contractor of a sports hall (lump sum of PLN 1,195,600 gross) claimed payment for a soil replacement (PLN 117,587.75), an additional connecting passage (PLN 50,525.78) and the removal of a collision with a water main (PLN 37,654.84). The action was dismissed in its entirety: with a functional description of the subject of the procurement it is the contractor who designs, it should have examined the ground before pricing, and the „additional” works flowed from its own design decisions. The conclusion is general — whoever answers for the design will not build a claim on the design’s gaps. The unjust-enrichment construction protects against someone else’s planning errors, not against one’s own.

The employer’s perspective

The slogan „lump sum and no annex” alone does not guarantee dismissal — but the defence has solid tools. The real lines are: proving that the works fell within the described scope and were covered by the tender pricing (the Kraków case shows what a difference a comprehensive description of the contract’s subject makes), contesting the value of the benefit (the lower-of-two-quantities rule, exclusion of VAT and mark-ups), the expiry objection (Article 409 of the Civil Code) and the objection of conscious performance without a reservation of return (Article 411(1)) where the contractor acted wholly outside the procedures and without coercion. An employer which itself initiated the disputed works and then hides behind form stands on weak ground — the case law consistently refuses to protect that tactic. A public employer will not defend itself with the procurement regime as such either: as the Court of Appeal in Białystok put it, the contracting municipality „cannot hide behind the provisions of public procurement law in order to evade the obligation to pay the amount corresponding to the value of the undue performance” (I ACa 69/17).

Frequently asked questions

Does the lack of purchase invoices kill the claim?

No. What is returnable is the objective value of the performance, not the costs incurred — the value of the works is proven with measurements, an as-built cost estimate and an expert opinion. Invoices help, but their absence does not close the road.

I performed the works knowing there was no annex. Have I lost the claim?

Usually not. If without those works you could not have completed the contractual works, and stopping the site threatened contractual penalties or termination, you acted to avoid coercion within the meaning of Article 411(1) of the Civil Code. Exclusion of recovery moreover requires full awareness, free of any doubts, that there was no obligation — in a dispute over the limits of a lump sum such certainty practically never exists. For the future: when starting disputed works, reserve the return of their value in writing.

The necessity protocol was signed by the site inspector. Do I have a contract for the additional works?

As a rule, no. The site inspector confirms the technical necessity of the works but is not authorised to make declarations of will for the employer — in the Kraków case protocols signed by the inspectors did not bring separate contracts into being. The protocol remains, however, the key proof of necessity and of the employer’s initiative. Always request confirmation of the arrangements by persons authorised to represent the employer.

Can I claim the margin I had assumed?

The claim covers the value of the employer’s benefit, not the contractor’s lost profit. It is safer to pursue the market value of the works performed (market rates carry the profit mark-up inside them) than to add profit separately. Full profit can sometimes be recovered by the damages route, where the source of the works lay in errors of the documentation supplied by the employer.

When does the claim become time-barred?

For a business, after three years, at the end of the calendar year (Article 118 of the Civil Code). The period starts not from the demand but from the day on which the demand could first have been made — practically from the performance (Article 120 § 1, second sentence). So do not postpone the demand, and remember that a statement of claim based on the contract interrupts limitation also for the restitution claim.

We agreed the works by e-mail, there is no annex — contract or enrichment?

Outside public procurement such an exchange may be an effective agreement, because between businesses the lack of written form does not block evidence (Article 74 § 4 of the Civil Code), and the price can be determined by analogy with Article 628 § 1. In public procurement there is no contract without a written annex (Article 432 of the Public Procurement Law) — what remains is the return of the value of the undue performance.

I am a public employer. Does procurement law protect me against payment?

No. The written-form requirement makes the agreement invalid, but for that very reason it opens the contractor’s restitution route — and the case law expressly refuses employers the right to hide behind procurement provisions against the obligation to return the value of an undue performance. The defence must be substantive: the scope of the contract, the value of the benefit, the premises of Article 411(1) of the Civil Code.

Quotations from Polish judgments and legislation have been translated by the author. All translations are unofficial. The Polish texts are authoritative.

State of the law: 10 August 2026.

Author: Artur Barczewski PhD — Polish attorney-at-law (radca prawny), conducts construction payment disputes for contractors and employers alike. About the author · Discuss your case →