There’s a moment in most promotional budget conversations where a cashback and a discount get treated as the same thing. Both are “$100 off”, so both get costed at $100 a unit. Anyone who has run a cashback knows that’s not how it plays out — and the difference runs in the brand’s favour. A meaningful share of the people who buy on the promise of a cashback never get around to claiming it. A discount, by contrast, is applied at the till every single time, whether the shopper even noticed the promotion or not.
That gap has a name, it has decades of research behind it, and it’s the single most important number in a cashback budget. It’s also routinely left out of the planning conversation, which is how brands end up either overpaying for a promotion or — worse — getting a nasty surprise when claims come in higher than the finance team assumed.
What is slippage in a cashback promotion?
Slippage is the percentage of eligible buyers who never claim the cashback they’re entitled to. Because unclaimed cashbacks cost the brand nothing, a cashback’s true cost is its face value multiplied by the redemption rate — not the face value itself — which is why a cashback almost always costs less than a discount of the same headline amount.
In The Shelf Truth we treat slippage as one of the core Budget Hacker levers, and it’s worth being clear-eyed about what it is and isn’t. It isn’t a loophole, and it isn’t something you should be trying to maximise. It’s a behavioural reality: people buy with good intentions, then life happens. The receipt goes in the bin, the claim window closes, the form gets abandoned halfway. Your job as a marketer isn’t to engineer that outcome — it’s to forecast it accurately and budget accordingly.
Why a cashback costs less than a discount of the same size
The arithmetic is simple: a discount reaches 100% of buyers, a cashback reaches only the ones who claim. What surprises most people is how far below 100% claim rates actually sit.
The best public data comes from a 2023 study by Tremendous and The Decision Lab, which found digital rebates of $20 or less were claimed only around 38% of the time, rising to roughly 50% for $50 rebates. Even generous offers leave a substantial share unclaimed. The academic literature backs this up: a Marketing Science paper on slippage in rebate programs ties the effect to present-biased preferences — the purchase happens now, the claiming effort comes later, and later is where good intentions go to die.
In the appliance cashback campaigns Trevor Services runs, we see the same pattern from the other side: actual claim volumes routinely land well under the pre-campaign forecast — sometimes at half of it or less. That’s not a failure of the promotion. It’s what cashbacks do, and it’s precisely why a $200 cashback on a $2,000 appliance can be materially cheaper to fund than a 10% discount — while looking just as generous on the shelf ticket.
There’s a second-order effect worth knowing about too. The same Tremendous study found the payment method changes what the offer is worth in the shopper’s head: mailed cheques and store credit shaved anywhere from $16 to $130 in perceived value off a $300 rebate compared with cash or a prepaid card. Pay people slowly and awkwardly and you’re funding a promotion the shopper mentally discounts before they’ve even bought.
How do you forecast a redemption rate?
You forecast a redemption rate from four inputs: the claim value, the effort required to claim, the length of the claim window, and the payment method — benchmarked against comparable past campaigns rather than gut feel.
Claim value is the strongest driver. The Tremendous data above shows claim rates climbing steadily with the amount at stake, which passes the common-sense test: nobody forgets a $500 cashback on a kitchen bundle the way they forget a $10 one on a kettle. Effort is the counterweight — every extra step between “I bought it” and “I’ve been paid” pushes some claimants out. This is the same mental maths shoppers run at the shelf, which we’ve written about as the 3-Second Equation, just applied at the claim stage instead of the purchase stage. The claim window matters more than most brands assume: a short window increases slippage but also increases complaints, and an overly long one makes the liability hard to close out. And payment method shapes both the claim rate and the perceived value, per the research above — which is why instant payouts via PayID have become the default recommendation on the campaigns Trevor Services delivers, ahead of cheques and slow EFT runs.
This is also where history beats intuition. A brand running its first cashback is guessing; a platform that has processed claims across many campaigns is not. It’s exactly the problem Trevor Services built Trudy for — pulling redemption patterns from thousands of historical promotions to put a defensible number against a new campaign’s forecast, instead of a hopeful one. If you’d rather do it manually, the honest starting point is your own last comparable campaign, adjusted for anything you’ve changed about value, effort, window, or payout. If you have no comparable campaign, assume more slippage at low claim values and less at high ones, and make sure your budget still survives if claims come in well above the forecast. Slippage is a forecast, not a guarantee — the brands that get burnt are the ones who booked the savings before the claims arrived.
Budget for slippage — don’t engineer it
Here’s the uncomfortable part. Once you understand that unclaimed cashbacks are free, there’s an obvious temptation: make claiming harder, and slippage goes up. Long forms, obscure claim portals, receipt requirements designed to trip people up, 14-day windows. It works, in the narrowest sense. It’s also a bad trade.
The shoppers who do fight through a deliberately awful claim process arrive at the payout annoyed, and the ones who give up remember why. We’ve called this the Insult Threshold — the point where the effort of claiming outweighs the reward and the offer starts costing you goodwill instead of buying it. A cashback exists to change purchase behaviour at the shelf; it does that job whether or not every buyer claims. Engineering slippage doesn’t improve the promotion, it just quietly converts a brand-building expense into a source of complaints. Where a cashback sits alongside the rest of the campaign — and what job it’s actually there to do — is a design question worth settling early, and Bamboo’s piece on campaign architecture is a good place to start on that.
The better posture: make claiming as easy as validation allows, pay fast, and let slippage be whatever honest slippage turns out to be. You’ll still come in well under the cost of an equivalent discount, and the people who claim will have had a good experience with your brand at the exact moment you handed them money — which is a rare and valuable combination.
If you’re costing a cashback against a discount and want a realistic redemption number to plan around rather than a guess, we’re happy to talk it through.
