A landmark damages claim against Mastercard that could put £100s in the pockets of around 46 million UK consumers has been filed at the Competition Appeal Tribunal (CAT) this morning.

The collective action is one of the first of its kind under the Consumer Rights Act 2015 and will make legal history in the UK by automatically representing the interests of ALL affected UK consumers – including those who've never used a Mastercard.

The claim revolves around former financial services ombudsman Walter Merricks' belief that Mastercard broke competition law for 15 years between 1992 and 2007 by charging excessive 'interchange fees' – the fees a retailer pays to your credit or debit card company when you use your card to shop. Merricks claims retailers would have then passed on these charges to consumers.

If the collective action is successful, there potentially would be paybacks for all affected (now thought to be in the region of 46 million consumers), but like all lawsuits there's no guarantee it will succeed. Mastercard has today stood by its original position by stating that it "firmly disagrees" with the basis of the claim and that it intends to "oppose it vigorously".  

Initial estimates valued the 'collective action', which is the biggest in UK legal history, at £19 billion. However, Quinn Emanuel, the law firm behind the claim, has since revised that figure to £14 billion after Mastercard provided fresh data.

What's happened today?

Quinn Emanuel has today filed over 600 pages of documents with the tribunal, setting out the detail of its claim against Mastercard.

This includes a statement from Merricks explaining why he is bringing the action and how he will manage it on behalf of consumers. There is also a report from independent expert economists and accountants that support the claim, and a detailed plan for managing the claim, including how the proposed class of 46 million consumers will be communicated with.

Merricks says: "The filing of this claim is the first step towards consumers obtaining compensation for what Mastercard did. I am confident that the CAT will authorise the claim to go forward, and I look forward to the opportunity to present our case. This is a watershed moment for consumer redress in this country."

What does Mastercard say?

A Mastercard spokesperson says: "Now that the claim has been filed, we will take time to review it in detail, however we continue to firmly disagree with the basis of this claim and we intend to oppose it vigorously.  

"We deliver real value through the benefits of security, convenience and consumer protection, and we are committed to investing in our payment services in order to continue to meet the rapidly evolving needs of all our customers."

What's MSE's role in all this?

MoneySavingExpert.com is quoted in the court papers filed today – we've agreed to adopt a 'watching brief' to follow developments on behalf of consumers.

Outlining our stance in the court papers, we state: "MSE is the UK's biggest consumer website, with 15 million users a month and over 11 million email addresses opted in to its weekly email send. The site supports and has lobbied for the introduction of UK class actions, rather than a 'don't ask, don't get', which penalises vulnerable consumers.

"MSE will help the millions of consumers potentially affected to understand the claim being filed on their behalf. MSE intends to follow the case as it goes along, keeping users updated as is editorially merited.

"If any compensation is awarded by the court, MSE will work to communicate and ensure that those who have suffered loss understand how to get the compensation the court has decided they are due."

Landmark legal claim seeking £14bn refund for UK consumers filed against Mastercard
46 million affected UK consumers could potentially be awarded an average of £304 each

What happens next?

Now the claim has been filed, there will be a certification hearing at which the tribunal will be asked to allow the action to proceed on a collective, opt-out basis. It's expected that this hearing will take place later this year.

Quinn Emanuel says a timetable will then be set to take the claim through to a trial that will likely happen around mid-2018, unless a resolution with Mastercard is made before that.

How much money might I get as a result of this claim?

To be perfectly frank it's still way too early to know whether or not the claim is going to be successful, let alone how much might be paid to consumers.

Quinn Emanuel now believes that Mastercard's high interchange fees cost consumers £14 billion during the period, and it's claiming for that amount. If awarded in full, this would equate to an average £304 for each of the estimated 46 million affected UK consumers (this is somewhat less than the initial estimate of £475 per person, based on previous figures).

Once again, it's important to remember that the case might not succeed. Even if it does, a much lower amount of compensation could be awarded – or the tribunal could find that not everyone in the class is eligible to receive it. At this stage, we simply don't know what will happen.

Quinn Emanuel previously told us it would employ a professional claims administration company to help and would try to make sharing out compensation "as easy as possible" – you wouldn't, for example, need to show old receipts of things you had bought.