How to calculate the true cost of a casino bonus
Updated 2026-10-20
Rates last checked 2026-10-20
The number on the banner is not what a bonus costs. “100% up to £100” can cost an operator a few pounds per new player or most of their first-month margin, depending on wagering, the games players choose, how many actually claim, and how the market taxes gambling. This guide walks through the calculation step by step, using the same model as the BonusBench bonus cost calculator, so you can reproduce every figure.
Why the headline value is the wrong number
Finance teams usually see bonus cost in one of two ways: the face value credited (which overstates cost, because much of it is never withdrawn) or the “bonus cost” line in the GGR to NGR bridge (which is accurate after the fact but useless when you are designing an offer). CRM teams need a forward-looking estimate: if 1,000 players deposit this month, what will this offer cost us, and does it pay back after tax?
To answer that you need five things:
- What the player is actually credited (the match on a typical deposit, not the maximum).
- How much of that value the house edge recovers while the player meets the wagering requirement.
- How many claimers complete wagering and how many forfeit the bonus.
- How many first-time depositors (FTDs) claim at all.
- How the market's gambling tax treats the bonus: as a deduction, as irrelevant, or as extra taxable turnover.
The formula
The calculator uses a deterministic expected-value model. For a deposit match:
wagering turnover = wagering multiple × bonus (or bonus + deposit)
real stakes = wagering turnover ÷ game weighting
edge recovered = real stakes × (1 − RTP)
cost per completer = min(max(0, bonus − edge recovered), max cashout)
gross cost per claimer = completion rate × cost per completer
gross cost per FTD = take-up rate × gross cost per claimer
Players who do not complete wagering forfeit what is left of the bonus, so they cost nothing in this model. Then the tax layer adjusts the gross cost:
GGR tax, bonus deductible: after-tax cost = gross cost × (1 − rate × deductible share)
stakes (turnover) tax: after-tax cost = gross cost + rate × bonus turnover
Finally the result is set against what a depositing player is worth. If a typical FTD generates a given GGR over your payback window, the operator keeps that GGR minus tax, minus the after-tax bonus cost, minus any acquisition cost. That is the net contribution, and it tells you whether the offer is ROI-positive.
Worked example: 100% up to £100 in the UK
Take a UK casino welcome offer of 100% up to £100 with 10x wagering on the bonus (the maximum the Gambling Commission allows since January 2026). Assume a £50 average first deposit, slots at 96% RTP and 100% contribution, 70% of FTDs claiming, 30% of claimers completing wagering, and £150 of GGR per FTD over the payback window.
- Bonus credited: 100% of £50 = £50 (the £100 cap does not bite).
- Wagering turnover: 10 × £50 = £500 of stakes.
- Edge recovered: £500 × 4% = £20.
- Cost per completer: £50 − £20 = £30.
- Gross cost per claimer: 30% × £30 = £9.00.
- Per FTD: 70% × £9.00 = £6.30, or £6,300 per 1,000 FTDs.
- UK Remote Gaming Duty is 40% of GGR and freeplays are not deductible, so the after-tax cost stays £6.30.
- Post-tax GGR per FTD: £150 × 60% = £90. Net contribution: £90 − £6.30 = £83.70.
The break-even point is just as useful. The offer pays for itself once a player generates £10.50 of GGR (£6.30 ÷ 0.6), which is £4.20 of NGR after the bonus. Below that, the player costs more in bonus and tax than they bring in. Load this example in the calculator.
How each term moves the cost
| Scenario | Real stakes to clear | Edge recovered | Cost / completer | Gross cost / claimer | After-tax cost / FTD | Break-even NGR |
|---|---|---|---|---|---|---|
| Base: 100% to £100, 10x bonus | £500.00 | £20.00 | £30.00 | £9.00 | £6.30 | £4.20 |
| 5x bonus | £250.00 | £10.00 | £40.00 | £12.00 | £8.40 | £5.60 |
| Wager-free | £0.00 | £0.00 | £50.00 | £50.00 | £35.00 | £23.33 |
| 10x bonus + deposit | £1,000 | £40.00 | £10.00 | £3.00 | £2.10 | £1.40 |
| 10x, 50% game weighting | £1,000 | £40.00 | £10.00 | £3.00 | £2.10 | £1.40 |
| 10x, £20 max cashout | £500.00 | £20.00 | £20.00 | £6.00 | £4.20 | £2.80 |
Four things stand out:
- Wager-free is by far the most expensive per player: £35.00 per FTD against £6.30, because every claimer converts the full £50. That is not a reason to avoid it, but the headline should be smaller.
- Applying wagering to bonus plus deposit doubles the turnover and cuts the cost to a third. Players notice, which is why the attractiveness score drops too.
- Game weighting works the same way: at 50% contribution players need £1,000 of real stakes to clear £500, so the edge recovered doubles.
- A max cashout only matters when the expected balance at completion is above the cap. Here it cuts the completer cost from £30 to £20.
Other offer types
Free spins are valued at their expected winnings, not their face value: 50 spins at 10p are £5 face, but at 96% RTP the player is expected to win £4.80. If those winnings carry wagering, the same edge-recovery logic applies to the winnings. Cashback is a percentage of expected net losses, capped. A free bet's value depends on the odds it is placed at, because the stake is not returned: a £10 free bet at evens with a 93% return is worth about £4.65.
| Scenario | Bonus value | Gross cost / claimer | After-tax cost / FTD | Per 1,000 FTDs | Cost % of post-tax GGR |
|---|---|---|---|---|---|
| Deposit match 100% to £100, 10x | £50.00 | £9.00 | £6.30 | £6,300 | 7.0% |
| 50 free spins at 10p, wager-free | £4.80 | £4.80 | £3.36 | £3,360 | 3.7% |
| 10% cashback on £200 losses, cap £50 | £20.00 | £20.00 | £14.00 | £14,000 | 15.6% |
| £10 no-deposit, 10x, £50 cashout | £10.00 | £1.20 | £0.84 | £840.00 | 0.9% |
The assumptions that matter most
Two inputs dominate: the completion rate and the expected GGR per FTD. Both come from your own data. Completion rates for 10x offers are far higher than for the 35x offers common before the UK cap; if you have no history, run the calculator at a few values and see whether the offer stays positive across them. Expected GGR should be the GGR a bonus-taking FTD generates over the window you use to judge payback, typically 30 or 90 days.
The model also ignores bonus abuse (multi-accounting, low-risk hedging on sportsbooks), payment costs and the incremental-revenue question: an FTD who would have deposited anyway is not “bought” by the bonus. Use the CPA field to load acquisition cost, and treat the result as the cost of the offer, not its full return.
Run your own numbers
Every figure above can be reproduced and changed in the bonus cost calculator, which also compares the same offer across two markets. Signed-in BonusBench users get the same engine inside the Promo Builder, can load any tracked competitor offer into it, and the AI brief quotes the after-tax cost instead of guessing it.
Work out the after-tax cost of your own offer
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Frequently asked questions
What does a casino bonus really cost the operator?
The expected amount players withdraw from it, after tax. For a 100% up to £100 UK welcome offer with 10x wagering, £50 average deposit, 96% RTP and 30% completion, that is about £9 per claimer or £6.30 per first-time depositor, far below the £100 headline.
How does wagering reduce bonus cost?
Every pound wagered returns the house edge to the operator on average. 10x wagering on a £50 bonus means £500 of stakes; at 96% RTP that recovers £20 of the £50. Higher wagering, lower RTP games and lower game weighting all increase the edge recovered.
Why do non-completers cost nothing?
Players who bust or abandon before meeting the wagering requirement forfeit the remaining bonus. Their play still generates revenue on their own deposit, but the bonus itself is never paid out.
Is a wager-free bonus more expensive?
Per pound of headline value, yes: every claimer converts the full value. A wager-free £50 costs £35 per FTD at 70% take-up, against £6.30 for the same offer with 10x wagering. Wager-free offers are usually smaller for this reason.
Does gambling tax change the cost of a bonus?
It depends on the market. Where the bonus is deductible from the taxable base, tax absorbs part of the cost. Where it is not, as in the UK, the operator bears all of it. On a stakes-based tax, wagering the bonus creates extra tax.
What is break-even NGR per player?
The net gaming revenue (GGR after bonus) a player must generate for the offer to pay back after tax. In the UK example it is £4.20, because the tax on GGR is not reduced by the bonus.
Sources
- HMRC: Gambling duty changes (Autumn Budget 2025)
- HMRC: Remote Gaming Duty, reforming the tax treatment of freeplays
- UKGC: changes to bonus promotions (wagering cap, mixed product)
This article explains a cost model. It is not tax, legal or compliance advice; rates and rules change, so check them with your adviser and regulator.