HMRC have published a guide explaining the concept of adjusted net income.

The concept is relevant to anyone liable to the:-

• income-related reduction to the higher personal allowances – for anyone born before 6 April 1948 with an adjusted net income of over £27,000 in 2014/15
• income-related reduction to the personal allowance – where someone has an adjusted net income over £100,000 (regardless of date of birth)
• High Income Child Benefit charge - where adjusted net income is above £50,000