Trusts and private companies are commonly used by families during their working lives. But issues often arise once retired.
See the attached article drawn from a real case study which appears commonplace.
The key points are:
If you have private trusts or companies or any other sort of potential assessable income or asset where the values cannot be easily and readily determined then plan early and think ahead. The process for assessment by the government is lengthy ,invasive, and they look back at many years of history.