s 28 Security for future advances, how to be charged
(1) A security for the payment or repayment of money to be lent, advanced or paid, or which may become due upon an account current, either with or without money previously due, shall be charged, where the total amount secured or to be ultimately recoverable is in any way limited, with the same duty as a security for the amount so limited. (2) Where such total amount is unlimited, the security is to be available for such an amount only as the ad valorem duty stamped thereon extends to cover; but where any advance or loan is made in excess of the amount covered by that duty the security shall for the purpose of stamp duty be deemed to be a new and separate instrument bearing date on the day on which the advance or loan is made. (3) No money to be advanced for the insurance of any property comprised in the security against damage by fire, or for keeping up any policy of life insurance comprised in the security, or for effecting in lieu thereof any new policy, shall be reckoned as forming part of the amount in respect whereof the security is chargeable with ad valorem duty.