The government is setting up a software swap-shop to allow government departments to use spare software without paying extra licensing costs.
The pool, the first of its kind, is designed to minimise waste caused when government departments take out licences for more copies of software than they use.
The software license pool will be a key component of a government-wide memorandum of understanding between the Treasury's Office of Government Commerce and Microsoft.
The Office of Government Commerce (OGC) Buying Solutions agency is expected to announce internally today a date for the deal to be signed, 18 months after the last memorandum of understanding (MOU) expired.
A source close to the negotiations said that re-usable Microsoft software licences were just a beachhead. The OGC had opened talks with all major vendors to agree the same terms.
He said it was the first deal of its type and made the UK the only country in the world whose government had agreed its own licensing terms with Microsoft.
A Microsoft spokesman said: "The current agreement expires on 30th April 2009, and we will be releasing information on the new arrangements when they are agreed."
An OGC spokesman said a deal was imminent and that April was a decisive month, but would comment no further. Since the last MOU ran out in January 2008, Microsoft licences have been bought under repeated six-month extensions of the old terms. Talks stuck over the pricing terms of the collaborative buying agreement.
The Operational Efficiency Programme recommended this week: "A further £1.6bn value for money savings could be achieved through the collaborative procurement of IT."
Read more on Business applications
UK government renews cloud discount pricing MoU with Microsoft
HPE signs 12-month hybrid cloud-focused MoU with UK government
IBM joins Google, Microsoft and Oracle in signing preferential cloud pricing deal with UK government
UKCloud signs MoU with CCS to provide public sector with discounted cloud pricing