620. Self-assessment.

Every personal return or trustee's return1 must include a self-assessment, that is to say:


    (1)     an assessment of the amounts in which, on the basis of the information contained in the return and taking into account any relief or allowance, a claim for which is included in the return, the person making the return is chargeable to income tax and capital gains tax for the year of assessment2; and


    (2)     an assessment of the amount payable by him by way of income tax, that is to say, the difference between the amount in which he is assessed to income