To view the Capital Allowances Calculator you click on this link. Alternatively you can also follow the navigation as shown below.
Navigation: Self Assessment >> SA100 >> Client Specific >> Edit >> Supplementary Pages >> Net profit(loss), Tax, allowances and Taxable profit(loss) >> Capital allowance
Select the 'Net profit(loss), Tax, allowances and Taxable profit(loss)' link which will open the prompt below.
Fill in all the details as required and save the form.