The answer is simple – there is no ‘penalty’ but any demand for rent and any service charge shall be treated for all purposes as not being due from the tenant to the landlord (until the correct information is served on the tenant).

Long-winded detailed answer…

S47 of the Landlord and Tenant Act 1987 requires that any demand for rent or other sums due under the terms of the tenancy must contain the name and address of the landlord. This includes if the address is not in England or Wales.

If the address is not in England or Wales, then the landlord must also provide an address in England and Wales at which notices (including notices in proceedings) may be served on the landlord by the tenant S47(1)(b).

If the demand fails to contain this information, then any part of the amount demanded which consists of a service charge (“the relevant amount”) shall be treated for all purposes as not being due from the tenant to the landlord at any time before that information is furnished by the landlord by notice given to the tenant. Unlike section 48 above a failure to provide the name and address of landlord in a demand for rent does not produce any ‘penalty’ in respect of rent.

In Beitov Properties Ltd v Elliston Martin [2012] UKUT 133 (LC) it was held that the address required to be provided in a demand for payment must be the landlords actual address and an agent address is not sufficient.

Reference: Guild of Residential Landlords article here