Apportionment

Each lease says what share of the costs that flat pays. It might be a fixed percentage (for example 12.5% for each of eight equal flats), a share by floor area, or "a fair proportion" decided by the landlord or manager.

Things to check

• Do the shares add up to 100%? If they add up to more or less, the leases may need varying. The tribunal can vary leases that don't make satisfactory provision for this (s.35).
• Different schedules. Some leases split costs differently for different things, such as the lift, the car park or the shops.
• Non-residential units. In an RTM building, if some units aren't held by qualifying tenants and the flats' shares come to less than 100%, the landlord pays the shortfall (s.103).

Rounding

When you split a bill in pounds and pence, the parts must add up exactly to the total. A good method is to round each share down and give the leftover pennies to the largest remainders, so nobody is over-charged and nothing is lost.

You can't change the shares just because it seems fairer. The lease governs until it is varied.