The admission - made as part of Microsoft's most recent quarterly financial results - comes despite the fact actual shipment figures for either the Surface RT or its bigger brother the Pro remain under wraps.
But while the Windows 8-powered Surface Pro sold out online in the run up to launch, the Surface RT has failed to entice consumers in an equally large number.
RT on the run
Indeed, news of Surface RT's dismal run comes just days after Microsoft announced an official price cut for remaining inventory.
Though largely praised for its design and build quality, commentators have long criticised the Surface RT due to Microsoft's decision to equip it with a cut-down version of the Windows platform.
Surface RT owners can download apps from the Windows Store and use Microsoft Office (which comes pre-installed), but unlike Surface Pro owners - they're unable to install third-party programs on the desktop.
As such, while many people view the Surface Pro as a well-equipped touchscreen able laptop, the Surface RT has struggled to find itself a place in the market.
Developers of RT-only apps have also complained that their titles have struggled to amass significant downloads.
New devices
News for the company as a whole, however, was far better. Microsoft recorded revenues of $19.9 billion in the quarter ended June 30, roughly in line with expectations on Wall Street.
"We are working hard to deliver compelling new devices and high value experiences from Microsoft and our partners in the coming months, including new Windows 8.1 tablets and PCs," said CEO Steve Ballmer of the results.
"Our new products and the strategic realignment we announced last week position us well for long-term success, as we focus our energy and resources on creating a family of devices and services for individuals and businesses that empower people around the globe at home, at work and on the go, for the activities they value the most."
Despite the write-down, Microsoft is expected to unveil updated Surface tablets in the run up to September and the launch of Windows 8.1, including a new Surface RT.
[source: Microsoft]
