Operators that display slot reload bonuses in whole pounds rather than as a percentage of the deposit have seen average top-up values fall 19% year on year, according to a comparison of 14 UK-licensed casinos run across the 2024–25 financial year. The same group recorded a 6.2 percentage point drop in reload uptake among players aged 25–34, the segment most likely to be shown a rounded balance. When a £4.73 bonus appears as "£5", players treat it as a fixed prize and stop chasing the remainder; when it appears as "4.73", they top up to clear it.

That is the finding, and it is less about generosity than about how a number is framed on a screen.

The rounding effect, measured

The data set covered 14 operators, all holding UK Gambling Commission licences, across 11 months from April 2024 to February 2025. Each ran at least one weekly slot reload — typically a 25% match up to £50 on a £20 minimum deposit. Seven displayed the bonus value rounded to the nearest whole pound in the deposit confirmation screen and the cashier widget. Seven displayed it to two decimal places.

The rounded cohort's average reload deposit came in at £27.40. The unrounded cohort sat at £33.81. That is a 19% gap, and it held when the two groups were matched on game mix, average session length and player tenure. It is not a small-sample artefact: the rounded group processed 214,000 reload transactions in the period, the unrounded group 198,500.

The mechanism is not mysterious. A £20 deposit at 25% yields £5.00 exactly, so the rounding is invisible at the headline tier. But the same offer on a £19 deposit yields £4.75, and on a £23 deposit yields £5.75. Operators that round those to £5 and £6 respectively are, in effect, telling the player the offer has a ceiling that does not exist. Players respond by treating the reload as a one-off gift rather than a ladder.

Where the 19% actually comes from

It is not uniform. Breaking the deposit distribution into bands:

• £20–£24.99: rounded cohort averages £21.10, unrounded £22.60 — a 6.6% gap
• £25–£34.99: rounded £28.90, unrounded £33.40 — a 13.5% gap
• £35–£49.99: rounded £41.20, unrounded £52.70 — a 21.8% gap
• £50+: rounded £58.60, unrounded £79.10 — a 25.9% gap

The effect scales with deposit size. That is the opposite of what most CRM teams assume. The conventional wisdom is that high-value players ignore display formatting because they already know the terms. The data suggests the reverse: the bigger the deposit, the more the player is doing mental arithmetic on the bonus, and the more a rounded figure short-circuits that calculation.

Why operators round in the first place

Two reasons, both defensible on their own terms.

First, regulatory presentation. Since the 2023 consumer duty rules came into force, the Commission has pushed hard on bonus terms being "clear and not misleading". A whole-pound figure is easier to state in a T&Cs line and harder to argue is buried. "£5 reload" reads cleaner than "£4.73 reload".

Second, front-end engineering. Many cashier widgets pull the bonus value from a pricing service that returns a decimal, then format it for display using a locale default of zero decimal places. Nobody chose rounding; it is a formatting inheritance from the payments layer, where whole pounds are the norm for transaction summaries.

The problem is that the same formatting logic applies to a value the player is meant to act on, not just read. A £4.73 bonus that displays as £5 removes the marginal incentive to deposit £19.27 more to hit the next tier. The player sees a settled number.

The wagering interaction

There is a second-order effect that matters more than the headline 19%. Rounded displays correlate with a 4.1 percentage point rise in bonus forfeiture — players who accept a reload, fail to clear the wagering requirement within the window, and lose the balance. In the rounded cohort, 31.8% of accepted reloads were forfeited. In the unrounded cohort, 27.7%.

Part of that is straightforward: smaller bonuses relative to deposit mean the player is less invested in clearing them. But there is also a completion-psychology element. A bonus shown as £5 against a 35x wagering requirement (£175 of play) is a clean target. A bonus shown as £4.73 against the same 35x (£165.55) is an untidy one. Players who see the untidy number are marginally more likely to play through it, possibly because the goal feels specific rather than nominal.

That is a hypothesis, not a proven causal link. The forfeiture gap could equally reflect the deposit-size distribution: bigger deposits in the unrounded cohort mean more players with the bankroll to complete wagering. But the effect survives controlling for deposit band, which makes the formatting explanation harder to dismiss.

What the numbers do not show

It would be easy to over-read this. The 19% figure is a comparison between two sets of operators, not a controlled experiment. The seven rounded operators differ from the seven unrounded ones in ways beyond formatting: three of the rounded group run their reloads on a Monday, four of the unrounded group run theirs on a Friday. Weekend reloads attract different player behaviour, and no amount of matching fully removes that.

There is also a selection issue. Operators that invested in decimal-precision cashier displays tend to be the same operators that invested in personalised bonus ladders, tiered reloads and dynamic minimum deposits. The formatting may be a symptom of a more sophisticated bonus engine rather than the cause of the uplift. Strip out the personalisation and the gap would likely narrow.

The cleanest way to test it is an A/B split within a single operator: same offer, same day, same player pool, decimal display on one arm and rounded on the other. Nobody in the sample had run that test. Until someone does, 19% is a correlation worth investigating, not a lever worth pulling blind.

The compliance angle nobody is pricing in

There is a regulatory question sitting underneath this that operators have not fully worked through. If displaying a bonus as £5 when the actual value is £4.73 changes player behaviour — and the deposit data says it does — then the display is materially influencing a commercial decision. Under the consumer duty framework, material information must be presented in a way that does not mislead. A rounded figure that inflates the perceived value of a bonus by 5.7% on a £19 deposit is a small distortion, but it is a distortion in the operator's favour, and it is systematic.

Nobody has brought a case on this yet. The Commission's enforcement to date has focused on wagering terms that are genuinely hidden, not on display precision that is technically accurate to the nearest pound. But "technically accurate" is not the test. The test is whether the average player is misled, and the average player, on the evidence here, is behaving as though the rounded number is the real one.

The open question is whether fixing the display costs more than it earns. Decimal precision reduces the headline appeal of a "£5 reload" in marketing copy, and marketing copy drives acquisition. But it increases reload deposit values by 19% among existing players, and existing players are cheaper to monetise than new ones. The operators running decimal displays have already made that trade. The rest are still rounding, and the data suggests they are leaving money on the table — or, depending on how the Commission reads it, taking it in a way they will eventually have to explain.