Apple faces a NZ$2.9 billion payout if a collective action lawsuit filed in the UK succeeds.
The claim, filed at the Competition Appeal Tribunal, says the US tech giant overcharged nearly 20 million customers for App Store purchases in the UK, reports Bloomberg.
The case alleges the 30 percent commission Apple charges is unlawful and an abuse of its market dominance.
Anyone who has purchased apps, subscriptions or in-app purchases since late 2015 is included in the lawsuit, unless they choose to exclude themselves.
Dr Rachael Kent, a lecturer in digital economy and social education at King's College London, is the lead claimant in the case and says Apple is abusing its dominance.
"Apple achieves this by slapping unjustified charges on its users," Dr Kent told the BBC.
"It would not be able to impose these exorbitant charges if competitor platforms and payment systems were allowed to compete."
Apple released a statement, describing the lawsuit as "meritless" and defending its 30 percent commission as being similar to that charged by other digital marketplaces.
It also highlighted that 84 percent of apps are free and many app-makers only have to pay 15 percent after it cut the commission in January for those earning US$1 million or less from the store.
This latest lawsuit comes as Apple faces off with Fortnite maker Epic Games in a US trial over the 30 percent commission.
The game was banned from the App Store after Epic introduced a way for users to circumvent Apple's in-app payment system, thereby avoiding commission.