A Seattle judge has ruled that Amazon must repay in-app purchases made without consent on Kindle and Android devices between 2011 and 2014.
The decision is a result of a successful FTC lawsuit, although its calls for a lump sum refund of over $25m was rejected for being ‘too high'.
The FTC argued that Amazon's in-app purchase drive, which kicked off in 2011, did initially not require that users input a password, even in apps aimed at children. This policy was changed in 2014.
The refund process must run for a year beginning from January 2017.
A similar ruling was made against Apple in 2014 when a FTC complaint led to a payout of over $32.5m to consumers the company billed for unauthorised in-app purchases.
"This settlement is a victory for consumers harmed by Apple's unfair billing, and a signal to the business community: whether you're doing business in the mobile arena or the mall down the street, fundamental consumer protections apply," FTC chair Edith Ramirez said at the time.
"You cannot charge consumers for purchases they did not authorize."