The round-up
Rees Calder · 26 April 2026 · 6 min read
You buy a coffee for £3.40. The app rounds up to £4.00 and sends 60p to charity. You don't notice. You definitely don't miss it. Over a year, those invisible 60p moments add up to roughly £150-300, depending on how many card transactions you make.
The round-up model is the smallest possible unit of giving, and that's precisely why it works. It exploits three well-documented behavioural biases simultaneously, making it one of the most psychologically efficient charitable mechanisms ever designed.
Why round-ups work (the behavioural science)
Mental accounting. Richard Thaler's foundational work on mental accounting (Journal of Behavioral Decision Making, 1999) showed that people categorise money into psychologically distinct budgets. Round-ups sit in a unique position: they're too small to register as "spending" and too automatic to feel like a "donation decision." They fall through the cracks of mental accounting entirely. The Commonwealth Bank of Australia ran a round-up charity pilot in 2019 and found that 83% of participants reported "not noticing" the deductions at all, even after 6 months.
The peanuts effect. Weber (1999, Decision Research) documented that people are risk-neutral for very small amounts. When the stakes are pennies, the psychological cost of deciding disappears. This is why lottery tickets sell despite negative expected value and why round-ups generate almost zero friction. The decision cost of giving 60p is effectively zero because the amount is below the threshold where deliberation kicks in.
Default bias. Once set up, round-ups run automatically. Madrian and Shea's landmark 2001 study on 401(k) auto-enrolment showed that default options have a 70-90% persistence rate. The same principle applies to round-ups: once activated, people almost never turn them off. The Commonwealth Bank pilot found 78% retention at 12 months, which is extraordinary for any financial behaviour change.
The scale arithmetic
The UK processes roughly 47 million debit card transactions per day (UK Finance, 2024). The average round-up per transaction is roughly 50p (since amounts are roughly uniformly distributed within each pound).
If just 10% of UK current account holders activated round-ups, that's approximately 5.5 million people. At an average of 25 card transactions per month (the UK Finance median), each generating roughly 50p in round-ups, that's £12.50 per person per month. Multiply out: roughly £825 million per year.
That figure is larger than the annual income of most major UK charities. The British Red Cross raises roughly £300 million per year. Cancer Research UK raises roughly £700 million. A 10% adoption rate for round-ups would create a new funding stream comparable to the UK's largest charities, generated almost entirely from money that nobody notices is gone.
Who's doing this
Monzo. The UK challenger bank launched round-up charity giving in 2022. Users choose a charity partner and round up every card payment. Monzo reports that activated users give an average of £8-12 per month, with retention rates above 70% at 6 months.
Sustainably. A UK app that connects to your bank account via Open Banking and rounds up transactions. Partners with multiple charities. Their 2024 data shows average donations of £11 per month per user, with the highest-frequency users (40+ transactions monthly) averaging £18.
Daffy. US-based donor-advised fund app with round-up features. Positions round-ups as the entry point to a broader giving habit. Their internal data (shared at Giving Tuesday 2024) showed that users who started with round-ups were 3.2x more likely to make a deliberate lump-sum donation within 12 months than users who started with a single gift.
Charity pots within traditional banks. Starling, Chase UK, and several building societies now offer round-up savings pots that can be directed to charity. The infrastructure exists across most of UK banking. Adoption is the bottleneck, not technology.
The "too small to matter" objection
The most common critique: isn't £10 a month too little to be worth the effort?
Three responses.
Aggregation. Your £10 doesn't matter. Five million people's £10 creates £600 million. The individual contribution is irrelevant. The systemic contribution is transformative. This is the same logic that makes voting rational despite the infinitesimal probability that your individual vote changes an outcome.
Habit formation. The Daffy data is the strongest counterargument. Round-ups function as a gateway behaviour. BJ Fogg's "Tiny Habits" framework (Stanford, 2019) predicts exactly this: tiny behaviours that require minimal motivation create identity change ("I'm a person who gives") that enables larger behaviours later. Round-ups don't matter for their direct financial impact. They matter for what they lead to.
The alternative is zero. For people who currently give nothing (roughly 35-40% of UK adults in any given month, per the CAF UK Giving Report 2024), round-ups convert zero to something. Any positive number is infinitely larger than zero. The perfect shouldn't be the enemy of the automatic.
Setting it up
If your bank offers it: Open your banking app. Look for "round-ups" or "spare change" in settings. Most UK banks now offer this. Activate it and choose a charity or giving pot.
If your bank doesn't: Download Sustainably or a similar Open Banking app. Connect your primary current account. Choose a charity. Set round-ups to active. The whole process takes under 5 minutes.
The optimisation move: Some apps let you multiply your round-up (2x, 5x, 10x the spare change). A 2x multiplier on a 50p average round-up becomes £1 per transaction, roughly £25 per month. Still below most people's noticeability threshold but meaningfully more impactful.
Cap it if it helps. If the open-endedness makes you uncomfortable, set a monthly cap (most apps support this). £15 or £20 per month is a common cap that keeps the giving substantial without any risk of budget surprise.
The compound picture
Round-ups alone won't solve global poverty. But they're the lowest-friction entry point into giving that currently exists. They cost nothing in attention, nothing in willpower, and almost nothing in money. They build identity and habit. And they generate data: after 12 months of round-ups, you have a precise record of your transaction patterns and a baseline giving number that makes your annual review (see "The year in numbers") trivially easy.
Start with the round-up. Build from there.
One sentence
Round up every purchase to the nearest pound, donate the difference, and never notice it's gone. The money is negligible. The habit it builds is not.
Sources used: Thaler "Mental Accounting Matters" (Journal of Behavioral Decision Making, 1999), Weber "The Peanuts Effect" (Decision Research, 1999), Madrian and Shea "The Power of Suggestion" (Quarterly Journal of Economics, 2001), Commonwealth Bank of Australia round-up charity pilot data (2019), UK Finance Payment Markets Summary (2024), CAF UK Giving Report (2024), Fogg "Tiny Habits" (Stanford Behaviour Design Lab, 2019), Monzo charitable round-up programme data (2024), Sustainably app aggregate giving data (2024), Daffy Giving Tuesday 2024 presentation data. Full links in the planning doc.