Surely you can't carry out and Independent Examination until the all the account accounting records are fully written up and you have a final set of accounts to examine.
So your charge will depend on whether you are just carrying out the examination or writing up the records and preparing the accounts as well.
If you're doing all the bookkeeping and preparing the accounts I would charge as per a normal business based on time/income depending on how you normally calculate your charges.
If you are just carrying out the examination (once the accounts are prepared), you need to assess the time it will take you based on the complexity of the charity's affairs. If this is difficult or you don't want to give them a fixed price, charge and hourly rate.
