The lease will provide you with all the information you need to know, however, you may need to pay attention to the language of the lease carefully. More often than not the lease will clearly state that the service charge is payable in advance by the tenant. If you can’t see the word advance mentioned clearly then look for the following.
Service charges in arrears will have very different language in their leases. The wording will centre around the tenant repaying the landlord for costs