I am not saying that the mechanic is legally bound to ask, but he is legally bound to sell the appropriate service (suitable for the purpose). A missing stamp means that there is no evidence that the previous servicing was done. Therefore, it is in the interests of the mechanic to include the corresponding clause into the contract (order, invoice, etc.). Otherwise, there is a risk that the servicing may be not suitable for the purpose, which means full refund plus possible damages.
freddymercurystwin wrote:... Please tell me where it says that if there is a missing service stamp then that should legally bind a mechanic into asking about previous service history? I will have a long wait!