Fifty-eight pence rounds up to sixty pence on a coffee at Pret, and Plum sweeps the difference into an investment pot before you have even finished the drink. Multiply that across a month of contactless taps and the pot fills with money you never consciously set aside. That is the entire pitch behind round-up investing apps, and by 2026 three names dominate the UK market for it: Plum, Moneybox and Chip. They are not interchangeable, whatever their app store screenshots suggest.
How the Round-Up Mechanic Actually Works
Each app links to your everyday current account — Monzo, Starling, NatWest, whichever bank you already use — and rounds every card transaction up to the nearest pound, sweeping the spare change into a separate pot. Moneybox pioneered this in the UK back in 2016 and still runs the cleanest version of it: round-ups accumulate until they hit £1, then get invested as a single batch, which keeps transaction fees from eating small amounts. Plum built a more aggressive version with rules-based top-ups layered on — it can move money based on your spending patterns, weather forecasts (genuinely, there's a "rainy day" rule), or a fixed percentage of any income deposit it detects.
Chip took a third path entirely. Rather than leaning on round-ups as the primary mechanic, Chip's AI-driven autosave algorithm analyses your account balance and spending rhythm over several weeks, then pulls out what it calculates you can afford to lose without going overdrawn. It's less visceral than watching individual coffee purchases round up, but for someone with irregular freelance income, it tends to move more money more reliably than round-ups alone ever would.
What Each One Actually Costs
None of these are free, and the fee structure is where most comparison articles get lazy. Moneybox charges £1 a month flat for its Stocks & Shares ISA and general investment account, plus a 0.45% annual platform fee and fund provider costs that typically run another 0.12–0.30% depending on the tracker fund chosen. Plum's free tier only round-ups into cash — to actually invest you need Plum Pro at £4.99 a month (or £9.98 for Plum Ultra, which adds a Mastercard debit card and cashback), on top of a 0.15% annual investment fee. Chip's Chip X plan sits at £5.99 a month and bundles investing with an "AI" savings feature and access to easy-access cash accounts paying competitive rates through third-party banking partners.
Run the numbers on someone investing £50 a month and the fee gap becomes real money over a decade. Moneybox's flat £1 plus 0.45% costs roughly £12 a year in the platform fee alone at low balances, dropping in percentage terms as the pot grows. Plum Pro at £4.99 a month is £59.88 a year before any investment fee — for someone only putting away £50 monthly, that's more than a full month's contribution eaten by the subscription. Chip X at £5.99 a month runs £71.88 a year. Below roughly £150 a month in contributions, the flat subscription fees on Plum and Chip outweigh what most people would pay a low-cost platform like Vanguard Investor, whose funds carry no platform fee below the account minimum threshold and an ongoing charge from 0.20%.
Where Each App Actually Wins
Moneybox is the better choice for anyone who wants round-up investing without a subscription eating a small pot. Its Stocks & Shares Lifetime ISA option is also the standout feature nobody else in this comparison offers in the same form — save up to £4,000 a year toward a first home or retirement and the government adds a 25% bonus, up to £1,000 annually, deposited directly into the invested pot rather than sitting uninvested in cash.
Plum makes more sense for someone who wants automation to go beyond spare change — the income-percentage rules and the "52-week challenge" savings pot genuinely move meaningful sums, not just pennies. But Plum Pro's £4.99 monthly fee only pays for itself once contributions climb past roughly £150 a month; below that, you are paying a subscription to invest less efficiently than a free brokerage account would let you.
Chip earns its keep with irregular income. A freelancer whose bank balance swings between £200 and £4,000 across a month gets more consistent saving from Chip's balance-reading algorithm than from round-ups, which barely register against income that arrives in lump sums rather than card taps.
The Tax Wrapper Question Nobody Asks Early Enough
Here's the part that trips up almost everyone switching from round-up spare change to something that resembles a real investment habit: which wrapper the money actually sits in matters more than which app you use. All three platforms offer a Stocks & Shares ISA, and for most UK taxpayers that should be the default choice over a general investment account, since gains inside an ISA are shielded from capital gains tax entirely. Yet Plum and Chip both default new users into a general investment account during onboarding unless the user actively selects the ISA option — a design choice that nudges toward the product with the higher ongoing fee percentage in Plum's case.
Anyone earning enough to use their full £20,000 annual ISA allowance elsewhere should treat round-up apps as pocket change management, not a serious investment strategy — the contribution sizes involved rarely justify the subscription cost once you're already disciplined enough to be maxing out an ISA through a low-cost platform like Vanguard or Hargreaves Lansdown.
The Catch With Fund Choice
All three apps route your money into a small menu of pre-built portfolios — typically a choice between "cautious," "balanced" and "adventurous," built from a handful of tracker funds and ETFs. None of them let you pick individual shares or a wider fund universe the way a self-select platform like Freetrade or Trading 212 does. That's a feature for beginners who'd otherwise agonise over fund selection, and a limitation for anyone who develops stronger opinions about where their money sits once the habit takes hold.
Moneybox's "balanced" portfolio, for instance, has historically leaned heavily on a small number of BlackRock and HSBC index trackers, with roughly 60% in equity funds and the remainder split between bonds and property funds depending on the risk tier selected. It's diversified in the textbook sense. It is not, however, a portfolio built with your specific goals, timeline or existing pension arrangements in mind — the app has no idea what's sitting in your workplace pension, and none of the three ask.
The Honest Verdict
Moneybox is the right starting point for most first-time investors, purely on cost — no subscription fee below its investing tier, a genuinely useful Lifetime ISA, and round-ups that quietly build a habit without demanding attention. Chip is worth the £5.99 monthly fee specifically for freelancers and anyone with unpredictable income who has tried and failed to save manually. Plum is hardest to recommend at its current price point unless the income-percentage automation and behavioural nudges are doing something for your saving habit that a standing order into an ISA wouldn't do just as well for free.
None of them replace a pension, and none of them should be the only account holding money earmarked for anything beyond five years out — the fund menus are too narrow and the fees, while modest per transaction, compound against small balances in a way that's easy to underestimate until the annual statement lands.