Sorry. I'm referring to an invoice provided by my solicitor regarding to the purchase of a property. New item described as "Service Charge Apportionment"? Not sure what charges are these?
Service Charge apportionment rules govern how charges relating to common services are shared out between each unit in a multi-unit development.
For example, in a development of 1, 2, & 3 bed apartments, the 3 beds will likely pay a little more than the 2 beds, who will in turn pay a little more than the 1 beds. Should all be detailed in the leasehold.
I think in this case it is the percentage of the annual charges refunded to the seller that they paid in advance at the start of the services year. So if the fees are due in April each year you will refund the seller the amount that is paid up to April 2020. It is usually worked out by getting the daily charge and multiplied accordingly.