Employed and self employed self assesment tax return

Is this self assesment calculation process correct for someone who is both employed and self employed? P60 paye gross income + self employment (-trading allowance) - personal allowance - paye employment tax and NI already paid = taxable amount. But prior to determining the liability, will hmrc put aside employment income which has already been taxed, and only apply tax (and Ni) to self employment income? As otherwise it looks like by being both employed and self employed you get taxed on employment net income + self employment (-pa).

Hi,
On the Self Assessment tax return you would declare the tax deducted at source against your PAYE income and this will be set against the tax due as calculated on the SA302. 
Thank you.