Estoppel in court 2026: no contradictory conduct

Author:

Олександр Сич

Published

1 April 2026

Estoppel is the prohibition of contradictory conduct: a party whose own actions created a reasonable expectation in another cannot later deny what it confirmed itself. In Ukraine the principle is derived from clause 6 of part one of Article 3 and part three of Article 13 of the Civil Code, and the formula “venire contra factum proprium” was settled by the Supreme Court in its judgment of 10 April 2019 in case No. 390/34/17.

On 10 April 2019 the Supreme Court, sitting as the Joint Chamber of the Civil Cassation Court, gave judgment in case No. 390/34/17 naming the doctrine of venire contra factum proprium (the prohibition of contradictory conduct) outright and tracing it to the Roman maxim “non concedit venire contra factum proprium”. Since then estoppel has ceased to be academic exotica: courts apply it in disputes about the invalidity of contracts, in tax conflicts and in commercial cases where a party performed an agreement for years and then suddenly claimed there had been no agreement at all.

The practical value of estoppel is that it works as a shield, not as a separate claim. You cannot file “a claim to apply estoppel”: the principle is raised in the defence, in objections, in a cassation appeal, and it forces the court to weigh the whole history of the parties’ dealings alongside whatever document the claimant has brought today. Below we set out which provisions estoppel grows from, on what conditions a court will take it into account, and what evidence has to be kept in advance.

Which provisions estoppel rests on in Ukrainian law

There is no separate article headed “estoppel” in the codes, and looking for one is futile. The principle is made up of four Civil Code provisions the court applies together. Clause 6 of part one of Article 3 names fairness, good faith and reasonableness among the general principles of civil law. Part five of Article 12 establishes the presumption of good faith: where the law attaches consequences to exercising a right in bad faith, a person is presumed to have acted in good faith until the contrary is proved.

Part three of Article 13 prohibits abuse of rights and allows a court to refuse protection to a person who acted contrary to that prohibition. Part three of Article 509 adds that an obligation must rest on good faith, reasonableness and fairness. Together these give the court a tool for assessing a party’s conduct over time, and that is precisely why estoppel in Ukraine remains a principle without a defined statutory test.

The procedural side rests on other provisions: Article 43 of the Civil Procedure Code requires participants to exercise their procedural rights in good faith, and Article 44 expressly calls abuse of them impermissible and allows the court to leave the relevant application unconsidered. Similar rules appear in Articles 42 and 43 of the Commercial Procedure Code and Articles 44 and 45 of the Code of Administrative Procedure.

Three conditions for a court to apply estoppel

The case law of the Civil Cassation Court requires three things to coincide. First, the party’s earlier conduct must have been clear and unequivocal: a signed acceptance act, a paid invoice, performance accepted, a letter acknowledging the debt. Silence alone is rarely treated as enough, because it admits of several readings.

The second condition is that the other party reasonably relied on that conduct and changed its position because of it: continued supplying, gave up security, let the limitation period run out. The third is that the reversal causes it harm that cannot be undone another way. Without harm the court confines itself to the ordinary assessment of evidence, and estoppel never appears in the reasoning.

Situation	Provision the court relies on	Consequence for the party that changed position	What the opponent must prove
A contract performed for years, then alleged to be invalid	Arts. 3, 13, 204 CC	the invalidity claim is dismissed	acts, payment orders, correspondence for the whole period
A transaction made without authority, but performance was accepted	Art. 241 CC	the transaction is treated as approved	the fact that performance was accepted after signing
Evidence not filed at first instance, produced on appeal	Arts. 83, 367 CPC	the court disregards the evidence	the absence of valid reasons for the delay
Systematic baseless recusal and adjournment applications	Arts. 44, 148 CPC	a fine of 0.3 to 3 subsistence minimums	repetition and the aim of delaying the hearing
A public authority reversed its own written position	Art. 3 CC, Art. 2 CAP	the decision is quashed as offending legal certainty	the earlier written explanation or approval

Substantive estoppel: when it is too late to challenge a performed contract

The commonest pattern runs like this: a party took delivery for two years, signed the consignment notes and paid in part, and when a claim came in for the outstanding balance it counterclaimed that the contract had never been concluded because an essential term was unagreed. The court takes Article 204 of the Civil Code on the presumption that a transaction is lawful together with the party’s actual conduct, and dismisses the counterclaim.

Article 241 works separately for agency: a transaction made by a representative exceeding their authority binds the principal if the principal approved it, and accepting performance counts as approval. A company that has booked in goods under a contract signed by an “unauthorised” manager loses the ability to rely on the lack of authority. That is why handling a commercial dispute starts by reconstructing the full chronology of the relationship and only then turns to the text of the contract.

Procedural estoppel: evidence filed late is evidence the court does not read

In procedure the principle bites harder, because it is backed by express deadlines. Article 83 of the Civil Procedure Code requires the claimant to file evidence with the statement of claim and the defendant with the defence; evidence filed out of time is disregarded unless the party proves it could not have been filed in time for reasons beyond its control. Article 367 repeats the rule for appeals.

The second line is objections to jurisdiction and to the composition of the court. A party that took part in several hearings without raising jurisdiction is later refused: the court treats silent participation as consent. The same applies to arbitration clauses, where silence at the start of the process closes off objections at the end. In complex cases a litigation lawyer fixes the procedural position at once, so that a later reversal does not become a ground to refuse protection.

Estoppel against the state and in tax disputes

The principle bites hardest where one party is a public authority. A taxpayer obtained an individual tax ruling, acted on it, and two years later an audit assessed additional liabilities because the authority had changed its position. Clause 53.1 of Article 53 of the Tax Code releases such a taxpayer from penalties.

The deadlines here are short, and they are forgotten more often than the principle itself. In July 2025 the Grand Chamber of the Supreme Court in case No. 500/2276/24 confirmed that a claim to quash a tax assessment notice is filed within six months, or, where the taxpayer first went through administrative appeal, within one month of the end of that procedure. Missing that month takes any argument about the authority’s contradictory conduct off the table, so challenging tax decisions is planned from the date of the decision, which is when the clock starts.

What a dispute involving estoppel costs

Estoppel is raised in an ordinary case, so it generates no fees of its own. A non-monetary claim by an individual carries a court fee of 1,331.20 UAH in 2026 and by a company 3,328 UAH; a monetary claim by an individual is charged at 1 % of its value, between 1,331.20 and 16,640 UAH. Filing through the Electronic Court subsystem reduces the fee by 20 %, an appeal costs 150 % of the rate and a cassation appeal 200 %.

Legal costs are recovered from the losing party under Article 137 of the Civil Procedure Code in an amount proportionate to the complexity of the case, so a detailed description of the work in the act matters as much as the figure itself. Indicative prices are collected on the legal services price list page.

How to raise estoppel in your own case

Draw up a dated chronology of the relationship: the contract, the first performance, every payment, every act, every letter. It is the sequence of dates that creates the picture of contradictory conduct.
Gather written confirmations of the opponent’s earlier position: reconciliation acts, letters of comfort, replies to demands, emails from the company’s own domain.
Set the argument out in the defence within the time the court set in its order opening proceedings: after that, new objections are accepted only for valid reasons.
Show your harm in figures: what continuing supply cost, what security you released, which limitation period you let pass because you trusted the opponent.
Plead limitation in a separate paragraph if the period has expired: the court does not apply it of its own motion, and after the first-instance judgment such a plea has no effect.
If the dispute has not yet reached court, try pre-action settlement of the civil dispute: the opponent’s written reply to a demand later becomes the strongest evidence of their earlier position.

Typical mistakes

Raising estoppel as a standalone claim. The court refuses to open proceedings or dismisses the claim, because Article 16 of the Civil Code provides no such remedy — the argument belongs in the defence.
Citing the name of the doctrine without the facts. A Latin formula without a chronology of the parties’ acts is rhetoric, and it never reaches the reasoning of the judgment.
Confusing estoppel with limitation. Limitation counts time, estoppel assesses conduct; an expired period is not cured by good faith, and bad faith does not extend a period.
Holding the strongest document back for the appeal “for effect”. Article 367 allows the appellate court to disregard it, and the strong document simply never enters the case.
Negotiating orally. An arrangement that appears in no correspondence is almost impossible to prove, and the opponent’s contradictory conduct leaves no trace in the file.

When you do not need a lawyer

If you have signed nothing, no dispute has started and the point is simply to pin down the counterparty’s position, you can manage alone: send a demand by registered post with a list of contents or to the company’s official email address and keep the reply. You can equally check whether court proceedings already exist through the Unified State Register of Court Decisions and the judiciary’s case index. Help is needed once a claim has been filed, once the value of the dispute exceeds the cost of representation, or where your own conduct also looks contradictory: there the estoppel argument may turn against you, and it is better neutralised before the first hearing, while the judgment is still to come.

Questions and answers

What is estoppel in plain words

It is a bar on denying what you yourself confirmed earlier by words or actions, where the other side relied on it and lost out because of your reversal. Ukrainian courts call it the principle prohibiting contradictory conduct.

Which article of the law sets out estoppel

There is no separate article. Courts derive the principle from clause 6 of part one of Article 3, part five of Article 12, part three of Article 13 and part three of Article 509 of the Civil Code, and in procedure from Articles 43 and 44 of the Civil Procedure Code.

Which Supreme Court judgment is treated as the leading one

The judgment of the Supreme Court, Joint Chamber of the Civil Cassation Court, of 10 April 2019 in case No. 390/34/17, where the doctrine of venire contra factum proprium is explained through the principle of good faith.

Can a separate claim be brought to apply estoppel

No. It is an objection to the opponent’s claim, raised in the defence, in submissions or in an appeal within a case that already exists.

Does estoppel work against a public authority

Yes, courts apply it where an authority confirmed its position in writing, a person relied on it, and the position was later changed. In tax disputes clause 53.1 of Article 53 of the Tax Code additionally releases the taxpayer from penalties.

Will estoppel save me if I missed the limitation period

No, these are different mechanisms. Estoppel assesses the parties’ conduct, limitation measures time; a missed period is restored only for valid reasons under Article 267 of the Civil Code.

What is the court fee in such a dispute

For an individual a non-monetary claim costs 1,331.20 UAH in 2026 and a monetary one 1 % of its value within 1,331.20–16,640 UAH. Filing through the Electronic Court reduces the sum by 20 %.

Can new evidence be filed on appeal

Only if you prove you could not have filed it at first instance for reasons beyond your control. That is expressly required by Article 367, and wanting to strengthen your position is not a valid reason.

How does estoppel differ from abuse of rights

Abuse of rights is broader: it covers any use of a right to another’s detriment. Estoppel concerns the narrower situation of reversing your own position after the counterparty has relied on it.

What if the opponent accuses me of contradictory conduct

Show that your earlier conduct was caused by mistake, deception or incomplete information, or that the opponent did not rely on it and suffered no loss. The absence of harm removes the argument entirely.

Sources

Defending your position on estoppel with Svarog

We reconstruct the chronology of the parties’ dealings, prepare the defence with the argument on contradictory conduct, gather the evidence of the opponent’s earlier position and carry the case through to cassation. A consultation costs from 1,500 UAH, a written legal opinion on the prospects of the dispute starts at 5,000 UAH, attending one hearing at 3,000 UAH, and full court representation in a civil case at 25,000 UAH.

+38 095 554-54-24 · Kyiv, 7 Khoriva Street (Podil) · Mon–Fri 9.00–18.00

Estoppel in litigation in 2026: the prohibition of contradictory conduct in practice