Any "mature" claim, i.e. a claimant's right for which the time limit for voluntary fulfillment/payment has expired (typically a claim for an unpaid invoice that is overdue) may be asserted in an action. However, the claim cannot be time-barred/void.

A claim is the right of one person (the creditor) to demand and effectively obtain specific payment from another person (the debtor). However, only a 'mature' claim, i.e. one where the debtor is in default against the creditor, is enforceable. Therefore, if the debtor of a mature claim does not voluntarily perform his obligation, there is no choice but to file such a claim in due time with the court (which will first assess whether the alleged obligation of the debtor actually exists).

It is not possible to sue for claims that have not yet matured, as the following example from everyday life illustrates: Mr. Novák borrowed CZK 10,000 from Mr. Svoboda and agreed to repay it by the end of the year. However, after a few days, Mr. Svoboda found out that he needed the money himself, so he turned to Mr. Novák and asked him to return the money; otherwise, Mr. Svoboda would sue him. Does he have the right to do so? A lawsuit would not succeed at such a time. Mr. Svoboda has no claim yet (the agreed maturity date has not yet come) and if he did file a lawsuit, the court would dismiss it as premature. Mr. Svoboda must therefore wait until the New Year (i.e. when the voluntary deadline for performance expires) and–if Mr Novák does not return the money himself–send him a pre-action notice and then sue him if necessary.

Just as a claim can be brought too early, it can also be brought too late. Claims cannot be successfully enforced forever, but must be brought before the court within the limitation period, after which the debtor may raise a statute of limitations objection, and the court will not allow the claim. Although the time-barred right still exists, it only exists as a 'natural obligation,' which the debtor may fulfill at their discretion (but it will not be considered performance without legal cause, and thus the creditor is not obligated to fulfill it according to their will). The debtor may continue to perform, but they do so entirely voluntarily (and it will not constitute unjust enrichment of the creditor).

Claims are usually brought in court, but there are other ways to enforce a claim in certain cases. For some claims, an arbitration clause has been negotiated, the parties may agree on an out-of-court settlement, or they may also conclude a notarial or enforcement agreement with a direct enforceability clause. The latter option is particularly useful where the debtor does not dispute the debt but needs to spread it over several instalments.