The licensee must ensure that if a computer system is used to retain trust records that: 

a. The computer programme cannot delete a ledger account unless the account balance is zero 

b. A record of the deleted ledger account is retained in visible form 

c. A back-up must be made at least monthly 

d. Transactions cannot be reversed; amendments must be made by entering a separate transaction to rectify errors 

e. (a) and (d) only 

f. (a) to (d)