Imagine an online slot whose jackpot should pay a certain amount but, because of a software fault, pays only a quarter of it. This is the British Gambling Commission's illustrative example, not a reported incident. The missing three-quarters would be a relatively simple debt to identify. A quieter fault—one that slightly reduces a frequent prize for months—poses the harder question: which players lost money, and by how much? The Commission's answer is to reimburse affected customers directly where possible, using exact game transactions if they can be reconstructed and an estimated shortfall when they cannot. Gambling Commission, remote game and software payment faults
That distinction matters more than the familiar “malfunction” line in a game rulebook. This article concerns confirmed faults in remote random-number-generator games offered under Great Britain's licensing regime. It is not a promise of a refund whenever a player has a losing session, and it does not describe a universal rule for casinos licensed elsewhere.
A bad run is not a broken game
A slot's theoretical return to player (RTP) describes the proportion of stakes the game is designed to pay back over very large numbers of plays. It is not the share any one person should recover. Our guide to what casino RTP means explains why short-term outcomes can deviate dramatically from that design without establishing a fault.
A payment fault is different. The Commission's examples include defective game mathematics that changes prize frequency or amount, a configuration that makes the live game behave differently from its rules, an exploited software vulnerability and prizes displayed incorrectly. The important evidence is not merely that someone lost, or that observed RTP sat below the advertised figure for a short interval. It is that an investigation identifies a defect affecting the game's fairness or return. Gambling Commission, fault types
Players' complaints can start that investigation. So can a software review, a supplier's discovery in an older codebase or monitoring of live game performance. Our story on why casino games are monitored after launch covers the detection stage. Here the clock starts later: the error has been confirmed, and the operator has to work out what it changed in real customers' results. Gambling Commission, identification routes
First, stop the faulty version and count the exposure
The Commission says confirmation of a game fault would usually coincide with disabling it. If it was left running during the investigation, it must be taken down while the fault is fixed and retested. A report to the regulator should not wait until every detail is known. The guide says a confirmed under- or overpaying game must be reported; its formal key-event instruction specifies reporting as soon as reasonably practicable and within five working days of becoming aware. Gambling Commission, reporting and remediation guide · Licence condition 15.2.1
The investigation has to identify the game and version, when the defective build went live, how long the fault lasted, the number of affected players and the money involved. The regulator asks for the difference between expected and actual RTP, the cause, why testing missed it and what will prevent a recurrence. If a business-to-business supplier reports, it must also say how many consumer operators offered the game and whether all were affected. A fault in one deployed configuration must not silently become a claim that every copy of a familiar slot title was broken. Our guide to different versions of the same casino game explains that version boundary. Gambling Commission, details required in a fault report
This is the less visible cost of the error: operators and suppliers need a defensible map from faulty code to sessions, customers and payments. The map determines whether they can calculate precise refunds or must estimate the missing return over a wider group.
The clean case: replay the transaction record
Where individual transactions show what the player actually received and what the correct game rule would have paid, the shortfall can be calculated round by round. The Commission makes direct reimbursement of affected players its default and expected remedy. Its quarter-paid jackpot example is designed to show a case with one identifiable customer and a knowable difference, not a precedent that every disputed jackpot is automatically payable. Gambling Commission, Approach A
That calculation still depends on proving which rules and version applied to the accepted round. The Commission's technical standards require reasonable steps to process and settle gambles according to published rules. When an unexpected system fault affects a customer, operators are to remedy it as soon as practicable and treat that customer fairly; its guidance mentions correcting an account manually where needed. Game rules and potential payouts must also be available before play. RTS 5, result determination · RTS 3, game rules and payouts
A screenshot may help establish what a customer saw, especially if the complaint is that the displayed prize was wrong. It is not a complete transaction history. The accepted stake, game-round identifier, result and account credit are the records that can test a precise shortfall. That is an editorial inference from the regulator's requirement to calculate exact transactions where available, not a claim that one particular casino stores or discloses each field in the same way.
The difficult case: the missing return is statistical
Suppose a frequent prize was configured to pay less than the game design required. Individual players may have seen different outcomes during the affected period; the operator may not be able to reconstruct every missed prize. The Commission's alternative method first estimates the difference in the game's theoretical RTP caused by the fault, then multiplies that percentage difference by turnover—total stakes taken while the defective version operated. Its example uses a 0.5 percentage-point reduction in RTP. Gambling Commission, Approach B
That formula estimates the aggregate amount underpaid. It does not prove that each person lost 0.5% of their own stakes, and it does not identify an exact missing prize on a named round. The Commission says every attempt should be exhausted to repay affected players directly; if that cannot be done, an alternative must prioritise affected consumers, avoid allowing the operator to benefit and include adequate disclosure. The exact allocation will depend on the fault and the available evidence. A neat sitewide “refund rate” without those qualifications would disguise the uncertainty the method is meant to handle. Gambling Commission, financial calculation and alternative remedy principles
If specific individuals cannot be identified, the regulator encourages efforts to return money to the group most likely to include them. Repayment should not require more gambling or a minimum spend. If customer repayment cannot be achieved in line with those aims, the guide says the operator should divest the profit to a responsible-gambling charity. That last route is a fallback, not a convenient substitute for finding and repaying players. Gambling Commission, remedy considerations
Who is responsible when a supplier wrote the code?
A player may know the casino brand but not the game studio, remote-game server or hosting company behind the slot. The Commission's fault guidance expressly covers business-to-consumer operators, business-to-business suppliers and game hosts. It asks a reporting supplier to identify which consumer operators used the affected game. That creates a cross-company investigation, not a reason to send customers around an invisible supply chain. Gambling Commission, scope and B2B reporting
For a customer, the practical first contact is the gambling business holding the account. The Commission's public complaints guide lists disputes about whether someone won, how much they were paid and IT issues, and directs customers to complain to that business first. The regulator itself says it does not decide individual gambling-transaction complaints. Contractual recovery between casino and supplier is a different question from the customer's explanation and remedy. Gambling Commission, complaint route
There is a communication nuance worth preserving. The game-fault guide says consumers should be told about remedial steps after the money has been returned, so the operator cannot turn the process into a promotion. RTS 5 separately says customers affected by errors should be notified as soon as practicable. The texts address different communications: an individual error notification and a broader account of a completed remediation. Neither makes a promotional “free spins” offer a substitute for returning money owed. Game-fault remedy guidance · RTS 5 customer-notification guidance
What can a player actually ask for?
For a disputed British online-casino round, the useful request is specific: identify the game and version, the date and round, the stake, the displayed outcome, the amount credited and the rule under which the result was settled. Keep screenshots and account-history records if available. Ask the operator whether it found a game or display fault, which period it affected and how any proposed correction was calculated. These are questions for an evidence-based complaint, not a guarantee that the player is entitled to a particular amount. RTS 2, displaying transactions · Gambling Commission, fault-report details
If the business does not resolve the complaint through its own process, the Commission says the customer can take it to a free, independent alternative dispute resolution (ADR) provider after eight weeks, or with a deadlock letter issued at the conclusion of the business's complaint process. The business should identify its ADR provider. This is a route for a transaction dispute, not a promise that every complaint will be accepted or decided in the player's favour. Gambling Commission, ADR guide
The central distinction is between an unfortunate outcome and a proven defective product. A losing session by itself has no missing balance to calculate. Once a genuine fault is confirmed, however, the question changes from “was this player lucky?” to “what did the broken game pay, what should it have paid, and who can be made whole?” For the regulator, a clean jackpot correction and a statistical underpayment are different accounting problems. For the customer, both demand the same thing from the operator: an intelligible answer backed by the game's actual record.
