It’s likely that you’ll lose your NCB if you switch to a company car. But if you’ll be using it for both business and personal use, some insurers might offer a ‘no claims driving’ policy, which can offer some sort of discount when you take out your own personal policy down the line. But not all insurers do this, so it’s worth checking your options before committing to a company vehicle. Your NCB is also valid for 2 years, so if you go back to a personal car within this time, your discount should still be valid.