Is it permissible for me to purchase a car from the company in installments, where the car remains registered in the company's name until full payment of the installments from the annual grant, and in the event of leaving the company, the car is appraised and the remaining amount is paid for me to own it, with no refund of previously paid amounts if I do not wish to take the car?

It appears the transaction mentioned is a lease-to-own contract, which has specific Sharia guidelines for its permissibility. These include: having two separate contracts (a lease followed by a sale or a promise of ownership), ensuring the lease is genuine and not merely a disguise for a sale, and that the leased asset's guarantee rests with the owner, not the lessee. Evaluating the car and selling it at its value at the end of the lease contract is permissible, provided the sale contract is separate from the lease. However, if the contract blends both sale and lease simultaneously, then entering into it is impermissible.