Why is the tax deducted for share options being restricted on the tax comp?

Client has got employment earnings of £63810, land and property income of £817 and Share schemes of £47161. There is also a grossed up pension contribution of £42688. User has entered a 50% tax deducted for share options of £23580 in the data entry screen but the tax computation is showing a restricted tax deducted of £14758. As it’s a rate restricted relief, the tax which is actually being charged on the share scheme income is calculated (assuming all other income is taxed first) Employment £63810 + land and property £817 = £64627 Less personal allowances: £64627 – £7475 = £57152 Basic rate band adjustment due to personal pension contribution: Basic rate band £35000 + grossed up pension contribution £42688 = £77688 20% basic rate – £57152 (other non savings income) 20% share scheme £20536 = £4107 40% share scheme £26625 = £10650 Therefore, tax charged on share scheme income – £4107 + £10650 = £14757 (difference due to rounding which has been ignored in the knowledge base)