If a vehicle is registered to a business on the V5C (logbook) instead of an individual, it can't be advertised as a private sale on Autotrader.
Even if you're not a dealer or in the motor trade, the vehicle must be advertised as a trade sale because it's considered a business asset.
If you haven't done so already, we'd also recommend contacting Consumer Advice on 0345 404 0506. They'll be able to help you with your rights and obligations when selling a company-registered vehicle.
Learn more about trade seller responsibilities with the Trading Standards Business Companion