Under the income tax code a child who is not the child of a claimant but who is in the custody of the claimant and is maintained by the claimant at his or her own expense for the whole or part of the year of assessment qualifies as a "child" for the purposes of:
(a) the income tax widowed parent and lone parent allowance (currently £2,150 and £2,650 respectively);
(b) the special income tax allowance for widowed parents in the three years following the year of bereavement (£1,500 in the 1st year, £1,000 in the 2nd year and £500 in the 3rd year);
(c) the child additions to the income tax exemption limits (currently £450 for the first and second child and £650 for the third and subsequent children); and
(d) health expenses relief.
It should be noted that this income tax treatment is based on the concept of the actual maintenance of the child not on whether the child is unofficially adopted.