As transactions have moved into the digital space, contracting now happens with a click on a shopping site, a subscription app, or a cloud services platform. In these contracts, service providers routinely include terms that fix in advance what a party must pay if it breaches its obligations, known as a penalty clause or liquidated damages clause. This has given rise to what may be called the electronic penalty clause: the same clause in substance, but appearing in an electronic contract and accepted and enforced by digital means. That raises new questions about its validity, proof, and limits. A penalty clause is, at its core, an agreement in which the parties fix the compensation the creditor will receive if the debtor fails to perform or delays performance. It spares the creditor from having to prove the amount of the loss and gives the relationship a degree of certainty. In digital contracts it takes several forms, including early-termination fees for ending a subscription before its term expires, late-delivery penalties for digital products or services, fixed damages for misuse of software or infringement of intellectual property rights, and forfeiture of a deposit or prepaid amounts upon cancellation. The first issue in this area is consent, since users often agree to terms with a quick click without reading them. Case law and legal scholarship distinguish between two kinds of acceptance. In the first, the user expressly clicks "I agree" after the terms are displayed, which is stronger evidence of knowledge and consent. In the second, the terms are shown through a side link and mere browsing is treated as acceptance, which is weaker and more open to challenge. The more prominent and clearly worded the penalty clause is, the more separate it is from other terms, and the more it is accompanied by the user's explicit acknowledgment, the stronger its position against a claim of ignorance. As for legal standing, electronic transactions laws recognize the validity of contracts concluded electronically and of digital signatures, so a penalty clause does not lose its force merely because it appears in a digital contract. Proving it, however, requires reliable records showing when acceptance occurred, who the contracting party was, and the text of the terms at the time they were accepted, because the party relying on the clause bears the burden of proving it exists. The law does not leave such clauses unchecked. In many civil law systems, the court has the power to adjust agreed compensation, reducing it if it is grossly excessive or if part of the obligation has already been performed, and the debtor may prove that the creditor suffered no loss at all. This oversight matters even more in digital contracts because they are often contracts of adhesion, drafted by the stronger party as a standard form that the user cannot negotiate. Courts therefore look skeptically at steep fees for cancelling a subscription, or at automatic renewal tied to a financial penalty without adequate notice. Such terms are treated as unfair and may be invalidated or modified under consumer protection rules. Automated enforcement adds a further challenge. Platforms may deduct the penalty automatically from a user's account or prepaid balance through programmed systems or smart contracts. Such automatic execution does not cure an unlawful clause and does not prevent the affected party from challenging it in court, since technology is a means of enforcement, not a source of rights. Nor is a penalty owed if the failure to perform results from force majeure or from the creditor's own fault, such as an outage or interruption on the platform itself. A practical difficulty also arises when the parties are in different countries, which raises disputes over the governing law and competent court. One legal system may allow a judge to adjust the penalty while another forbids it. It is therefore advisable for the contract to state clearly which law applies and which forum has jurisdiction.