I'll give the chair's ruling that it's not in order, Peter.
The effect of the amendment is to cancel the 50% taxable benefit that an employee could claim upon selling shares, resulting in an increase in taxation.
As House of Commons Procedure and Practice, third edition, states on page 772:
An amendment is also inadmissible...if it imposes a new charge on the people that is not preceded by the adoption of a ways and means motion or not covered by the terms of a ways and means motion already adopted.
I would therefore rule that the amendment is inadmissible, as it requires a ways and means motion.