Challenger bank Revolut has launched a feature that allows customers to save money by rounding up every transaction. But can spare change add up to a financial nest egg?
Revolut is the latest in a slew of challenger banks and apps that offer the option to save or invest your spare change.
We look at how much you might be able to lock away, and the pros and cons of this approach.
It's free to use, although you can also buy into a premium service for £6.99 a month, which includes unlimited foreign exchange, a premium card, overseas medical insurance and priority support.
For both types of users, Revolut now also offers a feature that allows you to round up transactions to the nearest pound and save the difference into a savings 'vault' - a separate area within the account.
So, if you spent £2.75, your account would be debited with £3 and 25p would be added to your vault. You can access your savings at any time.
If you'd rather not round up, you can opt to set up a recurring transfer or make one-off contributions.
But there's a drawback - Revolut doesn't offer interest on balances, so your money won't grow while you hold it within the current account or your Vaults savings.
A number of current account providers offer a similar 'save your change' function.
In March, launched a pilot with its 'Pots' savings feature. If you create a pot and name it 'Coin Jar', it will deposit your change with every transaction - but only when the balance of your account is more than £10.
Like Revolut, Monzo doesn't offer interest on balances or savings.
You can also download the Moneybox app to use with other banks' cards - you'll need to share your card details with it.
Moneybox allows you to choose your level of risk - cautious, balanced or adventurous - and your money will be invested in a portfolio that corresponds to one of these.
This means you stand to make a return if your investment grows - although you also risk losing your money. Moneybox analysis shows its 'balanced' portfolio grew by 18.7% in 2016 but just 2.4% in 2015 - and dropped by 4.8% in 2011.
Plum and Chip, meanwhile, are both apps that monitor your spending, then suggest how much you can afford to save or invest on a regular basis. You'll need to link these apps to your bank account.
With any option where you invest money, you may risk losing it, so only choose this option if you can afford to put your savings on the line.
Rounding up transactions makes saving seem easy - every time you swipe your card, you're adding a little to your pot.
But realistically, how much can you expect to save? I looked at my casual spending for the past month to estimate how well this approach would work for me.
Keep in mind the breakdown below is just a snapshot of how I use my debit card for day-to-day expenses - it excludes bills, bank transfers and spending on my credit card.
I spent £763.20 over the course of a month, meaning the apps would have put £36.50 into savings - working out to about 4.8% of my total spend. On average, I would have managed to save around £1.22 a day.
Over the course of a year, this would net a relatively modest £453.36.
Small, low-value transactions are most lucrative. My regular coffee spend of £1.35 would force me to save 65p, almost 48%.
By contrast, my splashiest purchase of the month - £53.99 on hiking boots - would earn me just 1p.
But the amount you'll stash away will vary from day to day - so if your budget is tight, you may prefer having more control over how much is saved and when you take it out.
For higher earners, this approach could let you build up a stash of extra cash - but if you have ambitious savings goals, it's unlikely to the best way to achieve them.
Because it only ever rounds up, your savings are dependent on the number of transactions you make, rather than the amount you spend - so to save more, you'd need to make a higher number of low-value transactions.
Setting aside a specific sum you plan to save - or a percentage of your earnings - is likely to better maximise your savings.
The lack of interest paid by several of the apps is also a problem. With inflation at 2.5%, keeping your money in a no-interest account means it's losing value in real terms.
If you're hoping to build up a financial cushion (that isn't risked by investment), you'd be better off choosing a high-interest account to stash your money in.
Which? Limited is an Introducer Appointed Representative of Which? Financial Services Limited, which is authorised and regulated by the Financial Conduct Authority (FRN 527029). Which? Mortgage Advisers and Which? Money Compare are trading names of Which? Financial Services Limited.