http://www.legislation.gov.uk/ukpga/2005/5/section/433/notesIncome taxTaxLegal servicesLegislationIncomeExplanatory Notes to Income Tax (Trading and Other Income) Act 2005Inland RevenueKing's Printer of Acts of Parliament2020-04-20 5 24 March 2005 1750 This section explains what is meant by an “excluded indexed security” referred to in the previous section. It is based on paragraph 13 of Schedule 13 to FA 1996. 1751 Subsection (1) explains that a security is an “excluded indexed security” if the amount payable on redemption depends on any future change in the value of certain assets or on the change in an index of the value of certain assets. 1752 Some securities provide for the investor to get back a percentage of his or her original investment if the value of the assets (or the index) fails to rise to a certain level. This will not prevent the security being a deeply discounted security provided the specified percentage is not more than 10% of the issue price (subsection (2)). This means that if £100 is invested the investor must get no more than £10 back, losing the other £90. Unless the investor can lose 90% of the original investment it is not an excluded indexed security but a deeply discounted security. 1753 Subsection (3) ensures that interest on redemption is ignored in the calculation under this section. It is clear that this is the intention of the legislation from the fact that paragraph 3(2)(c) of Schedule 13 to FA 1996 takes excluded indexed securities outside the definition of deeply discounted securities and that paragraph 3(6) of that Schedule (rewritten in section 430(4)) excludes interest from the general calculation of deep discounts. 1754 Subsection (4) defines “redemption period” for the purpose of this test. This definition differs from the one for the deeply discounted security test in section 430 to allow flexibility for the chargeable assets referred to in subsection (1) to be valued on dates other than, but close to, the issue and redemption dates. Likewise, an index of the value of chargeable assets may not be computed for the actual issue and redemption dates and some approximation is required. 1755 Subsection (5) defines “chargeable asset” for the purpose of this test. The underlying premise is that where the disposal of the asset whose value is linked to the security would be within the scope of capital gains tax, then disposals of securities fully linked to the value of such assets should also be subject to capital gains tax and excluded from the income tax regime. 1756 “Chargeable asset” is defined, in paragraph 13(6) of Schedule 13 to FA 1996, as an asset which on disposal can give rise to a chargeable gain for the purposes of TCGA. In order to make this test work it is necessary to make some assumptions about the asset (found in paragraph 13(7) of that Schedule) and these are set out in subsection (6). Section 100 of TCGA applies mainly for corporation tax purposes and unauthorised unit trusts are the only persons liable to income tax benefiting from subsection (6)(b).