Residential service charge demands must comply with the terms of the lease and with a number of statutory requirements. If demand is non-compliant, the service charge may not be payable by the lessee until the landlord fulfils his contractual and statutory obligations. In some cases, it may not be payable at all.
This checklist does not pretend to cover all of the points which will affect the enforceability of a service charge demand, but it is a starting point for ensuring that the landlord is getting the basics right.
Where a requirement is enshrined in statute, I have given the number of the relevant section, the name of the Act and any Regulations which underpin it. For reasonably current versions of legislation in the United Kingdom, try www.legislation.gov.uk.