A tribunal hearing in January will determine if a historic class action lawsuit against Mastercard can go ahead – the next stage in a landmark case which could potentially see 40 million consumers each receive £100s in compensation.

The 'collective action', launched by the former financial services ombudsman Walter Merricks in July this year, is one of the first of its kind since the Consumer Rights Act came into force in 2015.

It revolves around Merricks' claim 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, though Mastercard says it will "strongly oppose" the claim.

A 'case management conference' held in London today determined that a tribunal hearing on 18 January 2017 will decide whether the case can progress to a Competition Appeal Tribunal, a specialist court that hears competition law disputes, and also whether Merricks is the appropriate representative for the action.

Who could get compensation if this case succeeds?

What's most unusual about this legal claim is that it's a class action style claim being made on behalf of ALL affected UK shoppers, whether or not you've heard of the issue before or believe you were specifically affected.

If at any point between 1992 and 2008 you were of working age and were living in the UK, it is likely you'll be automatically represented in the case – even if you've never used a Mastercard. Quinn Emanuel, the law firm Merricks has engaged to take on the case, estimates approximately 40 million customers could be affected.

If the claim eventually succeeds at the Competition Appeal Tribunal, and as with all lawsuits there's no guarantee that will happen, everyone who's part of the collective action will be able to claim a share of the compensation.

What does Mastercard say?

A spokesperson says: "Mastercard continues to disagree with the basis of the proposed collective action and we will strongly oppose this claim in the event the court decides to hear the case.

"Our payments network delivers choice to consumers and real value through the benefits of security, convenience and consumer protection, and we are committed to investing in our services in order to continue to meet the rapidly evolving needs of all our customers."

How can I opt out of the lawsuit?

Unusually this legal action represents all affected UK shoppers – some 40 million in total – and you don't have to do anything to be part of it.

But you don't have to take part if you don't want to and a little more was agreed today about how that will work. The deadline for anyone who wants to object to the claim proceeding will be Thursday 22 December.

Although we still don't know exactly what the process will be, Quinn Emanuel has launched a website with details on how to opt out of proceedings, as well as FAQs and other information which can be found here.