You could post the bank payment of £300 (making a note of what it is for), to 2300 then after three months it would balance. So first month it would a credit balance of £950 and you would pay out £1150 leaving a debit balance of £200, next month it would show a credit balance of £1050 and you would pay £1150 leaving a debit balance of £100 then the final month you would have a credit balance of £1150 and pay out £1150 leaving the account balanced.