A unilateral set-off may extinguish a debt if the mutual claims are eligible for set-off and a definite declaration has been delivered to you. Maturity is generally required, but the Commercial Code provides exceptions in Sections 359 and 360. The mere fact that a counterclaim is disputed does not make it ineligible for set-off; its existence, amount and the other conditions must be examined. If the conditions are not met, the set-off does not extinguish the debt.
This is a common defence to invoice recovery: the debtor announces set-off of its own claim, typically damages, a price reduction or older invoices, then refuses further communication. Whether the set-off stands is assessed under fairly strict Civil Code (Act No. 40/1964 Coll.) and Commercial Code (Act No. 513/1991 Coll.) rules.
When unilateral set-off actually extinguishes debt
Where creditor and debtor have mutual claims for performance of the same kind, the claims are extinguished by set-off to the extent they overlap if either party makes a declaration of set-off to the other. Extinction takes effect when the claims became eligible for set-off against each other.
— Section 580 of the Civil Code (unofficial English translation)
Neither the other party’s consent nor a court decision is required. In case No. 2Obdo/34/2024, the Slovak Supreme Court reiterated that extinction by set-off does not depend on a judgment. An effective declaration operates retrospectively from the point the claims became mutually eligible, as explained in case No. 4Obdo/87/2021, so default interest also stops from then to the extent of the overlap. Between businesses, claims enforceable in court are eligible for set-off (Section 358 of the Commercial Code). Parties may agree to set off any mutual claims under Section 364, but this flexibility does not apply to a unilateral declaration.
The most common defect: set-off before maturity
An unmatured claim cannot be set off against a due claim, unless it is a claim against a debtor unable to meet its monetary obligations.
— Section 359 of the Commercial Code (unofficial English translation)
Both claims must generally be due; the law nevertheless provides, for example, the insolvency exception in Section 359 and permits set-off against a creditor’s unmatured claim under Section 360 of the Commercial Code. In case No. 5Obo/12/2019, the Slovak Supreme Court emphasised that damages become due only when asserted against the liable party through a demand, and set-off can be declared only afterwards. A debtor who never quantified damages or demanded payment but immediately announced set-off has therefore generally extinguished nothing.
What to check in a set-off notice
Work through four questions. Does the counterclaim exist, and on what basis? Merely asserting damages or a discount does not establish a claim. Were the maturity requirements met, or did a statutory exception under Section 359 or Section 360 apply? Does the declaration clearly identify which claim is set off against which, and for what amount? Was it delivered to you? A time-barred counterclaim cannot be unilaterally set off (Section 581(2) of the Civil Code). In commercial relations, limitation does not prevent set-off only where it arose after the claims became eligible (Section 358). See when a claim becomes time-barred.
How to respond
If a condition is missing, reject the set-off in writing with reasons, dispute the counterclaim’s basis and amount, and demand payment. Recovery then follows the ordinary unpaid-invoice route, including litigation, summarised in how to recover an unpaid invoice. If part of the counterclaim is justified, the dispute narrows to the balance.
How we can help
Our assignment and set-off service assesses notices and prepares reasoned responses, or structures your own effective declaration. We pursue the remaining claim through debt recovery and handle set-off litigation through court representation.
Do not file away a disputed set-off. Every month of silence may later be interpreted against you.
This answer provides general information on the law as at 10 September 2026. It does not constitute legal services or replace an assessment of an individual case. The details of your situation may differ. Book a consultation to discuss them.
