MonzoMetrics6 min read

Turning one balance into several

Mental accounting, implemented in software, with the numbers shown daily.

The surface: The balance screen and its supporting surfaces: Pots, round ups, category spending, budgets, and the instant notification after each card transaction.
What the user wants: I want to know how much I can actually spend this month without doing arithmetic every time I tap my card.

The instant notification

A card transaction produces an immediate push notification with the merchant, the amount and the updated balance.

Immediate feedback

Traditional statements delay the consequence of a purchase by days, which severs the link between action and result. Closing that gap to seconds makes spending feel like spending again. It is the single change that most alters behaviour, and it required no new financial product.

Pots

Money can be moved into named containers that sit outside the main spendable balance, with options to lock them until a date and to have bills paid directly from one.

Mental accounting

People already treat money as belonging to different purposes, and a single balance forces them to hold that structure in their heads. Pots make the structure real, so the rent money is visibly not spendable. Labelling is doing the work, because the money is fungible and the user's decision making is not.

Round ups

Card purchases can be rounded to the nearest unit with the difference transferred into a chosen pot automatically.

Painless saving through defaults

Saving fails because it requires a deliberate act at a moment when spending is more attractive. Attaching the saving to an act that has already happened removes the decision entirely. The amounts are small enough not to register as loss, which is precisely why the mechanism survives.

Automatic categorisation

Transactions are tagged into categories such as groceries, transport and eating out, with the app showing totals by category and allowing recategorisation.

Reduce the cost of measurement

Budgeting apps historically died because the user had to do the data entry. Categorising by default means the user's job shrinks to correcting occasional mistakes. A measurement system only changes behaviour if maintaining it is cheaper than ignoring it.

Budgets and the left to spend figure

Users can set category targets, and the app presents a summary of spending against them over the period.

A single number to steer by

Full transaction data is an audit trail, not a decision aid. Collapsing it into one figure gives the user something they can act on at the till. The design risk is that the headline figure has to be defined carefully, because whichever number is shown is the one people will optimise.

Committed spending

The app identifies recurring payments and subscriptions and shows what is still due before the next pay date.

Forecast over history

Knowing what has been spent is less useful than knowing what is already promised. Separating committed outgoings from discretionary balance answers the real question, which is what is safe to spend today. Most banking apps still only answer the historical version.

Where a number has to arrive to change anything

The monthly statement is more accurate, more complete and more carefully designed. It loses, because by the time it is read every decision it describes has already been made. A rougher figure delivered at the till is the only one standing where the choice happens.

What not to copy

Pots create a comforting illusion. Money in a pot is still available on demand, so a user who has mentally ringfenced rent can undo it in two taps, and the app does not make that undoing feel as consequential as it is.
Categorisation is approximate, and a supermarket trip that included a birthday present lands in groceries. Budgets built on noisy categories produce confident numbers that are wrong, which is worse than no number.
Gamified saving nudges and celebratory animations attach positive feeling to small acts that have a negligible effect on financial outcomes. Feeling good about round ups while carrying expensive debt elsewhere is an outcome the interface can produce without ever lying.
As the app has added lending, investing and paid subscription tiers, the same surfaces that exist to protect a user's money also carry offers. A screen that advises and sells at the same time has a conflict the user cannot see.

The takeaway

The metric that changes behaviour is the one that arrives at the moment of the decision. A perfect monthly report loses to a mediocre instant notification.

Finished the teardown? Bank it and the day counts toward your run.

Where the principles come from

Mental Accounting and Consumer Choice, Richard H. Thaler
Nudge: Improving Decisions About Health, Wealth, and Happiness, Richard H. Thaler and Cass R. Sunstein
Predictably Irrational, Dan Ariely

Written from public behaviour of the product, not from inside it. Interfaces change often, so treat the flow described here as of the time of writing and check the live product before quoting it.