Microsoft said that its ongoing legal spat with South Korean device number one Samsung sees its opponent taking action “in order to escape…royalty payments – amounting to billions of dollars”.

Documents released as part of the case show that Samsung paid the US computing giant $1 billion in patent licensing fees in the year to 29 August 2013, as part of a deal which fell apart following Microsoft’s acquisition of the Nokia handset unit.

With five years of the contract left still to run, clearly there is a lot at stake.

Microsoft even talked up the threat of the dispute, stating that it “faces the imminent risk of patent infringement claims by Samsung relating to the Nokia acquisition…and of a prohibited unilateral termination of the licence agreement by Samsung”.

The Windows company said that on hearing of the Nokia deal (announced on 3 September 2013), Samsung refused to pay its bill, due on 11 October 2013. When it finally made its payment, on 29 November 2013, this was done without a $6.9 million interest payment incurred by the delay, which has still not been settled.

Under the terms of the original agreement, Samsung agreed to make royalty payments to Microsoft for a period of seven years, with Samsung provided in return with credits for licensing its own technology for use in Microsoft products.  The amount due is based on the number of Android devices sold by Samsung during a twelve-month period.

Samsung is now arguing that smartphones made or sold by Microsoft units after the closing of the Nokia deal are not covered by the licence agreement, and it is therefore seeking damages.

Microsoft has also said that Samsung has asked the South Korean competition authority to change private contracts between the two – “thus, Samsung is attempting to convert a commercial contract dispute governed by US law into a Korean regulatory issue”.

Microsoft said that its initial partnership with Nokia was announced “more than six months” before the licence agreement was signed. It also noted that a clause in the Samsung agreement specifically covers businesses acquired by either party.

Microsoft is calling for a decision ruling that (among other things) the Samsung agreement covers the business acquired from Nokia; that the Nokia deal does not breach the terms of an agreement between the Microsoft and Samsung to “cooperate in the development and marketing of Windows smartphones”; and that the Nokia deal does not relieve Samsung of the obligation to make royalty payments.

And it also looking to prevent Samsung from seeking damages and royalty payments from Microsoft which are related to the Nokia deal.