According to the filing, for year two of the agreement, which spanned July 2012 to June 2013, Samsung had to pay Microsoft just over $1 billion in royalties. The amount is based on the number of Android devices Samsung sold and the prices it charged for them.
According to Microsoft, Samsung dragged its feet and made the payment late, so part of the reason it filed the lawsuit was to recover about $7 million in interest that it says Samsung still owes it.
Samsung has argued that Microsoft invalidated the agreement because it bought Nokia's handset business, so it's refusing to make further payments for this year and the coming years. That would mean billions in lost revenue for Microsoft.
Not surprisingly, Microsoft says its Nokia acquisition doesn't breach the agreement. It says there are "explicit provisions" that cover the acquisition of other companies.
The original deal was a cross-license agreement, which means Samsung was also agreeing to license technologies to Microsoft. With the deal broken, Samsung is threatening to sue Microsoft for using the Korean firm's technology.