How do I verify a Microsoft license is genuine?

Three checks. First, where you bought it — Microsoft Store, an authorized CSP partner, or a Volume Licensing reseller listed in the Microsoft partner directory. Anything else, including "deeply discounted" keys on marketplaces, is suspect.

Second, activation behavior. A genuine key activates on the first attempt and shows "Windows is activated with a digital license" (or "with a digital license linked to your Microsoft account") in Settings → Activation. A grey-market key may activate once and fail re-activation after a reinstall.

Third, the Microsoft 365 admin center for Microsoft 365 / Volume Licensing — your subscription should appear in the tenant's Billing → Licenses page. If it does not, you do not have a real subscription.

Still unsure?

Talk to a licensing specialist for a written, signed quote tailored to your environment.