The accumulated interest payable in respect of any national or war savings certificate issued by the Treasury through the Post Office or under the auspices of the Director of Savings, being a certificate under which the purchaser, by virtue of an immediate payment, becomes entitled after the expiry of a specified period to receive some greater sum, shall not be liable to tax so long as the amount of the certificates held by the person who is for the time being the holder of the certificate does not exceed the amount which an individual is for the time being authorised to hold under regulations made by the Treasury.

Where the currency of any national or war savings certificate has been extended under any Act, subsection (1) above shall apply with respect to any interest payable in respect of the certificate for the period after the expiry of the period referred to in that subsection up to the date on which it is repaid or redeemed as it applies to the said accumulated interest.