How to verify a Microsoft licence key's provenance before you pay
Legitimate second-hand licences and stolen keys sell side by side at similar prices. Provenance, not price, is the signal that matters.

Five signals of a bad key
None is conclusive alone; two or more together should stop the purchase.
- The seller cannot name the licence channel (retail, OEM, volume, MSDN)
- No written transfer or deletion confirmation from the original owner
- The listing shows unlimited stock of a single key type at a fixed low price
- Delivery is an activation script or a phone-activation walkthrough rather than a key
- No named legal entity, no VAT number and no returns address
What lawful resale looks like in the EEA
The Court of Justice of the European Union held in UsedSoft v Oracle (C-128/11) that the distribution right in a software copy is exhausted after the first sale within the EEA, allowing genuine resale of perpetual licences.
The conditions matter: the licence must be perpetual, sold as a whole, and made unusable at the source. A seller who can evidence that chain is on solid ground; one who cannot is selling you risk.
What Microsoft actually does with a blocked key
Microsoft does not disable your files or lock the machine. Activation simply fails or reverts to an unlicensed state with a desktop watermark, feature restrictions and nagging prompts.
That makes the seller's replacement policy the real product. A reputable reseller replaces a blocked key without argument; a marketplace listing usually vanishes.
Payment routes that keep your options open
Pay by a method with recourse. Within the EU, digital-content purchases have specific consumer rules, and card schemes allow chargebacks for goods not as described — both are far easier to use than chasing an anonymous seller.
- Keep the order confirmation, the key and any provenance statement together
- Test activation immediately, not weeks later
- Raise a replacement request before a chargeback — reputable sellers resolve it faster
Frequently asked questions
- Is it legal to buy a second-hand Microsoft licence in the EU?
- Yes for perpetual licences resold within the EEA, following the CJEU's UsedSoft ruling, provided the original copy is made unusable and the licence transfers as a whole.
- How can I tell if a Windows 11 Pro key is stolen?
- Look for an unnamed seller, no licence-channel disclosure, no transfer documentation and unlimited stock of one key. Legitimate resold licences come with provenance and a written replacement policy.
- What happens if Microsoft blocks my product key?
- Windows or Office reverts to an unactivated state with feature limits and a watermark. Your files are untouched. The fix is a replacement key from the seller.
- Can I get my money back on a digital licence?
- Usually yes. EU consumers have statutory rights for digital content that is not as described, and card chargebacks remain available. Ask the seller for a replacement first — it is normally quicker.
Keep reading on this subject
- EU Software Licence Resale Law Explainedeu software licence resale law
- Microsoft Activation Error Codes: Fix Ordermicrosoft activation error codes
- Windows 11 Activation After Hardware Changewindows 11 activation after hardware change