In theory, you don't have to pay a service fee to the 4S shop to buy a car.
Even if you buy a car with a loan, the service fee is provided by the bank, and the bank is the lender. As a service intermediary, 4S stores only cooperate with consumers to provide relevant bills to banks, so it is legal for 4S stores to charge fees for car loans. Merchants who charge "service fees" are suspected of fraud and can report their rights to the Industrial and Commercial Bureau.
If you buy a car through an auto financing loan in a 4S store, the 4S store needs to charge a handling fee, and you must clearly inform the consumer in advance, and you can only charge the fee after obtaining the consent of the consumer. Not saying it before buying a car, but saying it when paying, violates the principles of voluntariness, equality and fairness stipulated in the Consumer Protection Law.
If the handling fee is negotiated with the 4S store, the 4S store must also issue an invoice. Any behavior of charging fees in 4S stores is basically invoicing, otherwise it is illegal.
In fact, this fee is already a hidden rule, but it is called differently in different places. For example, it is called distribution fee, vehicle management fee and licensing fee. If you don't want to pay, there will be preferential policies. Even if there is a service charge, it will be compulsory to buy insurance.