439Amount of charge
(1)The taxable amount for the purposes of section 438 (charge on conversion of shares) is—
MV - DA
where—
MV is the market value of the shares into which the convertible shares are converted at the time of the conversion, and
DA is the total of any deductible amounts.
(2)For the purposes of subsection (1) each of the following is a “deductible amount”—
(a)the amount or value of any consideration given for the convertible shares or for the interest in them;
(b)the amount or value of any consideration given for the conversion;
(c)any amount that constitutes earnings from the employee’s employment under Chapter 1 of Part 3 (earnings) in respect of the acquisition of the convertible shares or the interest in them;
(d)any amount that is treated as earnings from the employee’s employment under Chapter 8 of Part 3 (taxable benefits: notional loans in respect of acquisitions of shares) in respect of the acquisition;
(e)if the convertible shares were, or the interest in them was, acquired by the exercise of a share option, any amount that counts as employment income of the employee under section 476 (charge on employee on exercise etc. of option) in respect of the exercise; and
(f)if the convertible shares were, or the interest in them was, acquired through a series of conversions each of which was a taxable conversion, the taxable amount for each conversion, so far as not falling within paragraph (c), (d) or (e).
(3)If, not later than the conversion, an event occurred in respect of the shares by virtue of which an amount counts as employment income of the employee under—
(a)section 449 (charge on occurrence of chargeable event), or
(b)section 453 (charge on increase in value of shares of dependent subsidiary),
that amount is a “deductible amount” for the purposes of subsection (1).
(4)Section 541(2) (effects of the EMI code on other income tax charges) also provides that an amount is to be regarded as a “deductible amount” for the purposes of subsection (1).
(5)For the purposes of subsection (1) the “market value” of shares means the amount that might reasonably be expected to be obtained from a sale of the shares in the open market.
(6)In subsection (2) “taxable conversion” means a conversion which—
(a)resulted in an amount counting as employment income under section 438, or
(b)would have done so but for the fact that the market value of the shares at the time of the conversion did not exceed the sum of the deductible amounts.
(7)The reference in subsection (3) to an event includes the expiry of a period.