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Certificate of Authenticity (COA)
In brief
A Certificate of Authenticity (COA) is a certificate of authenticity from Microsoft, usually a sticker on the device, that proves a lawfully acquired Windows license. Older devices also show the product key on it; on newer ones the key is stored in the firmware. For the resale of used PCs, the question of a valid license is important because it determines value and usability.
COA sticker and digital license
| Device generation | License proof |
|---|---|
| Devices with Windows 7 and older | COA sticker with visible product key |
| Devices from Windows 8 onward | Product key stored in the UEFI firmware; on the housing often only an authenticity label without a key |
| Refurbished devices | Refurbishers in Microsoft programs can install licenses with their own proof of authenticity |
Relevance for remarketing
A used PC with a valid Windows license tied to the device can be reused directly after erasure and a fresh operating system image, see Re-imaging. A company’s volume licenses, by contrast, do not belong to the device and do not transfer with it. How the end of support for Windows 10 affects the value of used computers is explained in our guide Selling used PCs after the end of Windows 10. At Second IT, purchased devices are erased with certification, refurbished and prepared for resale with a current operating system and security updates.
Frequently asked questions about the COA
Where do I find the Windows product key without a sticker?
On devices from Windows 8 onward, it is stored in the firmware. Windows usually detects it automatically when the same edition is reinstalled.
May I resell a device with a COA?
A preinstalled license tied to the device generally transfers with the device. Your company’s volume or subscription licenses are not included.
Does a COA sticker have to be removed before handover?
No. You should remove your own labels such as asset tags or inventory stickers, not the certificate of authenticity.
Does every PC still have a COA sticker with a product key?
No. Devices with Windows 7 and older carry a COA sticker with a visible product key. On devices from Windows 8 onward, the key is stored in the UEFI firmware. The housing then often has only an authenticity label without a key.
How do refurbishers license refurbished PCs?
Refurbishers in Microsoft programs can install licenses with their own proof of authenticity. A used PC with a valid Windows license tied to the device can be reused directly after erasure and a fresh operating system image.
Sell used PCs: erased, tested, remarketed.
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