The offer, details of which have been published on a Microsoft website, enables anyone purchasing an eligible Office 2010 product to upgrade for free once Office 2013 becomes available.
Microsoft declared it would allow those purchasing Office 2010 to upgrade to the new suite for free when it revealed that Office 2013 had hit its release to manufacturing (RTM) milestone earlier this month, but the terms of the offer have only just been detailed.
To take advantage customers must purchase, install, and activate one of the eligible Office 2010 products before the end of April next year. Furthermore, customers have until the end of May 2013 to upgrade, when the offer period expires.
Microsoft corporate customers with a TechNet or MSDN subscription will be able to download the Office 2013 suite from mid-November onwards.
But the software giant has yet to specify a general availability date for the next-generation Office, other than it is expected to hit retail outlets sometime in the first quarter of 2013.
Microsoft said it can notify users of Office 2013 availability if they sign up for an email reminder.
Office 2013 includes touch-optimised versions of the familiar Office applications to support tablet users, and also features greater integration with Office 265 and other cloud services to store documents and other user data.